According to multiple reports, Doc Rivers will be returning to coach the Celtics next season. Rivers has three years remaining on his current contract, having inked a five-year contract extension in May, 2011. Celtics general manager Danny Ainge confirmed the news to Gary Washburn of the Boston Globe, saying, “We’ve got a coach everybody would love to have.”

Celtics guard Avery Bradley made the NBA’s All-Defensive Second Team — the first such honor of his three-year career. He received 10 first-place and five second-place votes from the NBA’s 30 head coaches, and his 25 total points trailed only Tony Allen (53) and Chris Paul (37) among the league’s guards.

If next season’s Celtics team does not start Kevin Garnett at power forward, prepare for a long, dark stretch. Without KG patrolling the middle in green and white, feel free to reintroduce yourself to the lottery, long losing streaks and the empty promise of rebuilding.

If Kevin Garnett walks away from the Celtics following their first-round playoff loss to the Knicks, it’s going to mark the beginning of a long rebuilding era for the team. (AP)

While you miss the scowls, intensity and blocked shots after the whistle, remember that the decline of the Celtics is more complex than the team simply aging. The major problem is the Celtics actually ask Garnett to do more now than they did during the NBA finals run in 2010. Despite his age (37 on May 19) and contract (2 years, $24.3 million), Garnett still is a premier power forward and a critical piece for a team chasing a championship.

“Back in Minnesota, Kevin used to say, ‘I want to live beyond my contract,’ ” new Timberwolves president (and former coach) Flip Saunders told WEEI.com. “That meant whatever he was getting paid, whenever someone would see him in a game or in a practice, he wanted to live up to that contract and then play beyond that.”

Garnett has done exactly that in his six seasons in Boston. His playoff averages (35 minutes, 12.7 points, 13.7 rebounds, his highest playoff average since 2004) against the Knicks also demonstrated that quality basketball remains afloat in his veins. Surrounded by the right players, Garnett still can help Boston contend for a championship. After watching Garnett for 18 seasons, Kevin McHale — who drafted Garnett in Minnesota with the No. 5 pick in 1995 — still is amazed by his former student. Garnett was the first player in 20 years to go directly to the NBA from high school, and McHale recently reminisced about Garnett’s rookie training camp in Minnesota, when the 19-year-old was only a couple of months removed from his senior prom.

“I loved the kid the first day of practice,” McHale said. “He laid on the floor after his first training camp — laying on the ground with nothing left — and I said, ‘We’ve got to go again tonight.’ He went, ‘Huh?’ I said we did two-a-days, and he was like, ‘Oh my.’

“But that night he came and he laid it on the ground, played on the line, laying on the ground, playing on the line. At the end, he was laying on the ground, and I said to him, ‘Now we do two again tomorrow.’ He looked up at me and said, ‘Man, this is going to be a job.’ He hasn’t changed since then, he’s just got better.

“His ability to compete at a high level for such a long time, his love of the game, his competitive nature,” marveled McHale, “it really is fun to watch.”

Competing at a high level for an extended period of time in the National Basketball Association takes a rare talent. It is a skill that is difficult, but far from impossible. The highest standard of excellence has been set by the Spurs, a team with an aging superstar in soon-to-be-Hall-of-Famer Tim Duncan. Far from the best of friends, Garnett and the 37-year-old Duncan share very similar basketball philosophies, a fact not lost on Spurs coach Gregg Popovich.

“They can look in the mirror and realize they’re both the same in so many respects as far as how they run their lives in the NBA and how they’ve run their careers,” Popovich said during his last trip to Boston. “They’re both competitive as hell, they both understand the game, they both love being on the court, and neither one of them is really that excited about the hoopla that is all around it, but they’ve also endured by taking care of their bodies and what they do in the summertime to take care of their bodies.”

Popovich also stressed that both Garnett and Duncan, even at an advanced age for an NBA superstar, are the centerpieces for their teams’ success.

“They’re each the base of each team no matter how you slice it: they’re each the heart and soul of their respective teams, and they can both feel very good about the stamp they both made on the league,” Popovich said. “They’re very, very similar.”

The Spurs have kept their core of Duncan-Manu Ginobili-Tony Parker together while adding the necessary ingredients to remain among the league’s elite over the past decade. Outside of briefly entertaining the thought of a Parker-Jason Kidd trade a decade ago, San Antonio remained far more loyal to its trio of superstars than the Celtics. Like any general manager, Danny Ainge has a difficult job, but constant trade rumors have hurt overall loyalty to the team. Ray Allen turned down a far better contract to remain in Boston and instead opted to sign with the Heat, the Celtics’ main rival, for two reasons. One was an opportunity to win another championship, but the second, and more painful, reason is the fact that the Celtics made multiple attempts to trade Allen during his final three seasons in Boston. Allen cannot be blamed for abandoning the Celtics when the organization failed to stay loyal to him. Paul Pierce also has been a constant target of trade rumors, and even Garnett — who holds a no-trade clause — was part of the speculation this past February in what would have been an extraordinary coup for the Clippers.

Both Duncan and Garnett became free agents after the 2012 season. When San Antonio — like the Celtics, an older team with a dynamic point guard — dropped four straight games in the Western Conference finals and ultimately lost in six games last spring to Oklahoma City, there was no talk of blowing up the Spurs and starting over. Yet immediately after the Celtics, who took the eventual NBA champion Heat to the brink of elimination, lost Game 7 in Florida, rumors began swirling that the team would go through an extreme makeover. The media scrutiny admittedly is different in San Antonio than it is in Boston, but the Celtics’ perceived willingness to move their top players is a far different M.O. than the tight-lipped philosophy in San Antonio. Loose lips sink ships, or, in this case, lead to crashes. San Antonio last won a title in 2007, a year before the Celtics hoisted the Larry O’Brien trophy, but the Spurs continue to supply Duncan with able-bodied bigs like Tiago Splitter, Boris Diaw, DeJuan Blair and Matt Bonner. The Celtics, on the other hand, brought in two players, Shavlik Randolph and D.J. White, from the Chinese Basketball Association to protect Garnett. Duncan actually missed key stretches of the Spurs’ Game 1 win over Golden State with flu-like symptoms, whereas a serious lack of depth causes the Celtics to crumble when KG is not on the floor.

The idea of starting over, sans Garnett, currently is en vogue after a plane crash of a series against the Knicks in the opening round of the playoffs. The Celtics are fully aware of the challenges of rebuilding. However, most teams are unable to move aging stars for anything but cap space, so unless a team brings in elite players, there simply is no way to rebuild quickly in the NBA. This current Celtics crash — which included dropping the first three games against New York and playing more like the 2007 lottery incarnation during the majority of the embarrassing Game 6 loss at the Garden — actually began in 2010. Planes, like NBA teams, rarely crash because of one major error. The standard accident customarily involves seven consecutive errors. Unfortunately for the Celtics, their fall to mediocrity also included seven costly mistakes. Individually, none were too costly. When added together, these errors from a lethal cocktail. The primary error was failing to surround Garnett with the necessary pieces to be at his best, but others included the costly free agent signings of Rasheed Wallace and Jason Terry, a lack of loyalty to Ray Allen, the devastating decision to let Tony Allen walk, failing to provide complements through trades and the draft, and asking Garnett to produce more each season as he aged. The last potential mistake is the misconception that it is time to part with Garnett and start anew in Boston. This wouldn’t mark the first time a team misjudged Garnett.

“When McHale and I went to watch Kevin work out in Chicago, all the players in the lottery were invited,” Saunders said of the 1995 pre-draft workout. “We went there with the idea that the top four guys were the ones coming out from college: Joe Smith, Antonio McDyess, Jerry Stackhouse and Rasheed Wallace. We probably had more of a need for a guard, so we thought we might take Stackhouse. Our idea was to watch Garnett work out and make a big deal out of this high school kid. We were hoping the other lottery teams would become intrigued by him, so then someone would take him and one of those other college players would fall to us.”

That plan changed, of course, the moment the Minnesota brass laid eyes on Garnett.

“Well, we went there, and after about five minutes Kevin McHale and I looked at each and said, ‘This is our guy.’ His workout was off the chart, but when you watched him — when you really stood back and watched him work out — the way he moved offensively and defensively, if you didn’t know, you would have thought he was a 6-foot-3 or 6-foot-4 guard.”

Saunders also touched on Garnett’s appreciation for the game. Garnett’s mother, Shirley, taught her son the importance of hard work and respect. For a time, Shirley Garnett drove a forklift in a factory before becoming a hairdresser and opening her own beauty salon. As with many parents, the original plan for her son did not pan out. Mrs. Garnett wanted Kevin to go to college and become a social worker. He chose a different path, but the lessons she taught her son about the value of working hard evolved into a trait that still carries over to Garnett’s play. An NBA superstar who shares the basketball, sets screens, rebounds and prides himself on his defense is almost as rare as the Loch Ness Monster.

“He has great respect for the game and he’s carried that through his whole career,” said Saunders, who coached Garnett for 10 seasons in Minnesota and served as a coaching consultant with the Celtics during the home stretch of the 2012 season. “The respect that he has for the players who played before him is really special. Bill Russell, for instance, is always ‘Mr. Russell,’ and he knows he’s able to do what he does for a living because of what the past players were able to do. His professionalism sets the tone for his teams.

“He’s a very unique player and the most competitive guy I’ve ever been around. His game preparation starts at the time he wakes up in the morning. Everything he does is built to prepare so he’ll have success when he walks out on the court. He has a very, very high basketball IQ, the highest I’ve ever been around. There were times when we were looking at scouting reports, and Kevin would reference a game from six years prior where we used a strategy that was really effective in stopping an opponent. When you look at everything he can do, guarding ones, twos, threes, fours and fives, the way he rebounds, the way he can score, his assists, he’s the only guy in the NBA’s history to average 20-10-5 four years in a row, and he’s still always trying to get better. He’s trying to pass that along to his teammates for the success of his team, too.”

Garnett is six points away from passing Reggie Miller for 14th in all-time points scored. He is 10th on the list of most rebounds and 18th for most blocks. Even after playing in a total of 1,454 games, he remains the lynchpin for the Boston Celtics. The entire organization will become a lot more ordinary with the loss of KG. Instead of the C’s trading him or allowing him to retire, a better team needs to be built around him. Garnett’s basketball ideology and skill set, unlike most of the players in the league, are irreplaceable. He’s even more intense in practices than he is in games, and does not have an agenda when goes out to the court to play. The man simply understands how to play the game the right way. If there is an open teammate, he finds that jersey. If he is supposed to make a play, he makes that play. As Garnett ages, he needs the Celtics to do their job and place the proper support around him. Yes, Garnett’s body is beginning to betray him, something the soon-to-be 37-year-old power forward has in common with every big man to ever play the game of basketball. Pierce, after turning over the ball 32 times in six games against the Knicks, clearly is not the same the player who jumped out of a wheelchair to dominate the Lakers in the 2008 finals. Yet both men still are commodities in a league that specializes in exactly that: commodities. The problem, again, lies in the pieces that surround their Hall of Fame talents.

Similar to his final years in Minnesota, Garnett is surrounded by a diminishing crop of talent each year. Just like the case with those Wolves teams, the burden to lead the Celtics to prominence is unrealistic. Boston proved in 2008 (and, if it weren’t for the final six minutes during Game 7 in Los Angeles, the same would be said for 2010) that championship basketball is played with transcendent superstars who must be surrounded by upper-echelon teammates. A team needs its trio of stars, as well as a high-quality supporting cast. The Celtics went the opposite direction during the 2010-11 and 2011-12 seasons, but especially so during the 2012-13 campaign. Highly touted draft pick Jared Sullinger lived up to his reputation of talented but injury prone after he was unable to play the final four months of the season because of back surgery. Chris Wilcox fell out of the team’s rotation, and Brandon Bass’ inconsistency harkens memories of Ed Pinckney. This comes after the C’s appeared to find a good fit in Greg Stiemsma in 2011-12. The C’s stockpiled guards (but still failed to field a quality point guard come playoff time; Terrence Williams, another Chinese Basketball Association import, delivered weak numbers at the point in the Game 6 loss to the Knicks: zero points, one turnover and a team-worst minus-15 in a dozen minutes) yet failed to produce any true reinforcements for the greatest all-around power forward in the history of pro basketball.

A major chink in the Celtics’ armor occurred after the 2010 playoffs concluded when the team did not re-sign defensive menace Tony Allen. For those who followed Allen’s progress during his formative NBA years in Boston, his development into one of the league’s elite defenders in Memphis has been difficult to stomach. Even though he barely got off the bench in the Game 7 loss to the Lakers (he played only 5:20), Allen’s proven defensive energy and scoring ability necessitated he be part of the team’s future.

Nate Robinson was another piece on that 2010. Robinson recently was spotted dropping 23 points in a single quarter against the Nets and scoring 27 points in Chicago’s Game 1 victory in Miami over LeBron James’ Heat. Along with Glen Davis, Robinson demonstrated he was precisely the type of scorer the Celtics needed off the bench when he helped the Celtics defeat the Lakers in Game 5 of the 2010 finals (12 points, 2 assists in 16 minutes). Robinson and Doc Rivers may never share the same philosophy on the sport Dr. Naismith created, but former Celtics assistant Tom Thibodeau is getting the most out of Robinson. The Bulls lost Derrick Rose, their franchise point guard, but addressed his absence with the combination of Robinson, Kirk Hinrich and Marquis Teague. The loss of Rajon Rondo and Leandro Barbosa never was adequately addressed by the Celtics, nor was the team ever able to replace the production of Ray Allen. Jason Terry did not produce as expected (Terry’s first season in Boston was a failure on the court, as he delivered the lowest averages in points and assists since his rookie season in 2000), and Courtney Lee struggled through an inconsistent season that is on par with his career. The Celtics simply never addressed major concerns at center. The biggest problem with the Jeff Green-Kendrick Perkins deal was dismissing the protection and support Perkins provided Garnett in defending the paint. When asked recently what makes Garnett such so tough, Perkins just laughed.

“Everything,” Perkins said. “He can stretch the floor, think the game. KG’s still in great shape, man. You say he’s older, but his turnaround is difficult to stop. You can’t say nothing but future Hall of Famer.”

Perkins’ teammate, Kevin Durant, agreed with the assessment on Garnett.

“He’s so long and athletic, he can just shoot over the top,” Durant said. “Sometimes you get your hand up, but it’s just not enough.”

LaMarcus Aldridge, the 27-year-old All Star power forward for the Blazers, conceded that even if Garnett is nearly 10 years his senior, KG still is extremely difficult to defend.

“He’s going to come out real hard, so you need to try to match his intensity,” Aldridge said. “You just try to contain him as much as you can out there.”

The league-wide respect for Garnett is at an all-time high. Opponents begrudgingly admit he still is a force, as well as recognize the fact that he is the rare NBA superstar who is willing to do all the blue-collar work on the floor.

“He just plays every minute,” Timberwolves coach Rick Adelman said. “He’s going to compete the whole time he’s on the court, and he is one of the few guys who is a star that does the little things for his team. Helping to set screens, whatever it takes, he’s going to do that and he’s been that way since he’s been in the league. I don’t think he cares how many points he scores, all that matters to him is if he wins.”

And this is the type of player the Celtics can afford to let go?

Just in case the point needs further reinforcement, Doug Collins also shared some wisdom on the kid from Chicago’s Farragut Academy.

“I remember when I was in Detroit, Kevin was coming out of high school,” Collins recalled. “Not a lot of people were allowed to watch him work out, but I happened to know his agent and got an interview with him at a hotel. I walked in the hotel and met with him, and the guy knew more about me than I knew about myself. I knew right then this was a young guy who had an incredible respect for the game and was going to be an incredible player. He’s become a terrific leader. I don’t know if there’s anybody in the NBA who loves to play more than he does, or loves to compete more than he does.”

Whatever it takes, through hell or heartbreak, Boston needs to put on another full-court press to keep Garnett active in a Celtics uniform. Garnett mentioned that Paul Pierce was a big part of his decision to come to Boston in the first place, and the two have complete trust in one another on the court. Despite Pierce’s contract, and even in the wake of his disastrous 4-of-18 shooting performance in the final game against the Knicks, he and Garnett still provide this team with a legitimate championship foundation. The bottom line remains that the team needs to somehow find a way to surround them with a better supporting cast. Al Jefferson and Paul Millsap may seem like pipe dreams, but Ainge put together an extraordinary offseason when he brought in Garnett, Ray Allen and James Posey in the summer of 2007. Ainge once demonstrated the ability to draft remarkably well; he put the team in position to succeed with picks like Tony Allen (drafted at No. 25 in 2004), Delonte West (24 in 2004) and Jefferson (15 in 2004), while engineering draft-day moves for Rondo and Perkins. Yet the Celtics, who also pulled off draft-day trades for second-rounders Leon Powe (2006) and Glen Davis (2007), have little to show for recent drafts (J.R. Giddens and JaJuan Johnson are two notable busts). A failure to find reinforcements in the draft is another critical factor in the team’s decline. So, whether it is accomplished through a trade (Jeff Green holds value and could be moved for a premier big man) or free agency, the Celtics need to bring in better players around Garnett. With assistant general manager Ryan McDonough accepting the GM position in Phoenix, it is worth speculating whether the Celtics and Suns could be trade partners (a trade of Green for Marcin Gortat and Jared Dudley, in case you were wondering, does fit salary cap parameters for both teams).

Kevin Garnett has played over 55,000 minutes in his career, Paul Pierce over 45,000 and Jason Terry nearly 40,000, and Rajon Rondo is recovering from an anterior cruciate ligament injury that has forced other point guards (Derrick Rose, Ricky Rubio) to rehabilitate for over a year before resuming play. The crowd can lift those players, but they do not have the lift in their legs they once did. The Celtics need to move Green and Terry to create room to sign some legitimate post players. If not, the consequences of letting Garnett leave will be disastrous. The team’s once incredibly efficient offense is a thing of the past. In the 2008 championship season, the Celtics averaged over 100 points per game and, shooting the fewest shots in the NBA, they ranked fourth in field goal percentage and fifth in 3-point percentage, got to the free throw line, forced turnovers and had a killer defense. The team needs to find a new way to win, but Garnett must remain an important part of the mix in order to succeed.

“His enthusiasm for the game is infectious,” Saunders said. “He’ll do whatever he can on the court to gain an advantage, whether it’s physically or mentally. He’s always been a guy who talked a lot on the court. He’s not afraid to challenge his own players, and he demands players play up to his level on a daily basis. He is the greatest all-around power forward ever. It’s very rare to find a player like that.”

Here’s hoping the Celtics find a way to keep him.

On his final weekly appearance on Salk & Holley of the 2012-13 NBA season, Celtics president of basketball operations Danny Ainge called the recent St