Before the Celtics went on their four-game road trip the mood around the team was one of unease. What had happened to this once-dominant team that we had seen in early November?

They were winning games, mostly, but they were making things very hard on themselves, and the double-digit blowouts were just a distant memory.

One week later the Celtics will return to Boston as the hottest team in the Eastern Conference, winners of seven straight and proud owners of a four-game road sweep. They capped it off with an impressive 105-87 win over the young and exciting Oklahoma City Thunder, a day after gutting out a win over the old and stodgy San Antonio Spurs.

On the trip the Celtics returned to their dominant defensive roots and played smart, efficient basketball on the offensive end. They will have a well-earned three days off before their next game back at the TD Garden against Milwaukee on Tuesday.

Here are three things we learned:

THE RETURN OF KG

No player epitomizes the Celtics reversal of fortune on their road trip better than Kevin Garnett. When last we saw him in Boston he was angrily stalking off after reporters questioned the health of his knee and generally looking like he might be on a slow descent.

Yes, there was a game-winning shot against the Knicks and then a perfect shooting night against the Raptors, but still, there were concerns that this might be as good as it got for Garnett this season.

Then came the road trip. Garnett took 46 shots in the four games and made 35 of them. He might not shoot that high a percentage at Waltham against air with Tom Thibodeau feeding him the ball.

More than the shooting, however, has been Garnett’s play on defense and his willingness to attack the basket. He looks more athletic, more spry and much quicker off the floor.

Garnett is likely to continue to have some ebbs and flows as the season wears on, but if you were given the choice of taking 15 points, seven rebounds, and 20 games played out of 20, you would have gladly taken it back in October.

PAUL PIERCE CAN TEACH KD A FEW THINGS

Without question Kevin Durant is one of the most exciting young players the NBA has seen in some time. He is a naturally gifted scorer with the wingspan of a pterodactyl and the shooting touch of Craig Hodges, if not quite the range. Yet.

But Durant still has a few things to learn about being a complete superstar, especially on the defensive end. While Durant was pouring in 22 first-half points on 9-for-12 shooting he was allowing Paul Pierce to score at will on the other end.

In the second half when the Celtics adjusted by running multiple defenders at him, Durant insisted on shooting tough shots instead of passing to his teammates. To be sure, a “tough” shot by Durant might be a better scoring opportunity than an open one by Thabo Sefolosha. But Durant will learn, as Pierce did, that there’s more than one way to impact a basketball game.

Durant finished with 36 points, but zero assists. Pierce, meanwhile, scored all 21 of his points in the first half and seemed intent on exposing Durant’s weaknesses on the defensive end. Then in the second half Pierce backed off almost completely, allowing Garnett and Rajon Rondo to work their two-man game again and again, while ratcheting up the pressure defensively. 

Durant will likely improve his overall game as the talent around him improves. At this point it’s really him and Russell Westbrook for the Thunder offensively, and it’s an approach that has allowed Oklahoma City to compete night in and night out.

“Durant is awesome,” Doc Rivers said to reporters after the game. “He’s going to lead the league in scoring very soon. He’s going to lead this team to the playoffs very soon. It’s coming.”

All that is true. One just hopes for the sake of the league that he continues to develop his entire game because he can be a player who carries the NBA in the not do distant future if he is able to put it all together.

A-PLUS FOR THE GAMEPLAN

It will get lost in the final score, but Rivers had a solid gameplan for the Celtics and they executed it throughout. Without starting center Nenad Kristic, the Thunder are very thin up front and the Celtics took advantage of that by pounding the ball inside and working the offense from back to front.

Kendrick Perkins overwhelmed Nick Collison, who is a solid backup 4 but no more than a solid backup 4, for 13 points and eight rebounds. Collison spent most of the night in foul trouble, which caused Oklahoma City coach Scott Brooks to call on young and raw Serge Ibaka to play 20+ minutes.

OKC’s matchup problems were only beginning. Jeff Green, who is a 4 man in a 3 man’s body, had no chance to stay on Garnett and Garnett took advantage working his patented left shoulder fadeaway and losing him for easy dunks on back cuts.

Even Rasheed Wallace established himself down low in the paint before drifting out to knock down a pair of 3’s in the fourth quarter.

In all the Celtics scored 48 points in the paint and got to the line 15 times in the first half. Without a shot blocker inside (perhaps a role Durant can assume as a weakside defender) the Celtics were able to drive at will. They also racked up nine offensive rebounds and generally controlled the glass.

Rivers also had the Celtics ready to run from the opening tip, matching the young Thunder’s energy with a well-executed transition game in the first quarter.

Considering this was the last game of the trip and their fifth game in a week, Rivers and the Celtics deserve credit for staying focused and executing.