Time was short Monday afternoon after the Celtics practice, which was just as well because the answers to the problems that have plagued the team for the last two months were as up in the air as the impending plane ride to Detroit.

Paul Pierce suggested the problem lay in maintaining focus.

“It’s a combination of things,” Pierce said. “Second and third efforts have really hurt us. The first effort is there every time. It’s got to be that second and third effort that helps you win ballgames, and gets loose balls and helps you rebound.”

Doc Rivers suggested the problem was more immediate and that a better initial effort and execution would help. A cynic would suggest that they’re both right.

In the absence of quantifiable truth, or blame, everything is seemingly up for debate with the Celtics.

Are they too old and too beat up? Are they talented enough to compete with the Cavaliers, Magic, Lakers and Nuggets of the world? Have they tuned out the coach? 

All we have are the words of the members of the organization and they swear that none of those factors are in play, especially the last one. So what is it? What has caused the Celtics to turn from world-beaters in the first 28 games of the season to the Charlotte Bobcats over the last 29? 

This is what we know: Since Christmas, the Celtics have played 29 games and lost 16. That’s not a trend or a slump, and it’s not a small sample size. If you want to believe that the first 28 proved something, then you can’t discount the next 29’s impact.

They have played 11 games during that span against teams with the top 10 records in the NBA and they are 1-10 against the elite, with the lone victory coming by a point against a Kobe-less Laker team. That suggests a lack of talent, or at least a lack of healthy talent.

They have played 10 games against the bottom 10 teams in the league and have managed to win only six of them. Compounding that was the dreadful loss to the Nets, at home no less, on the day after Danny Ainge ripped them in the local papers. That suggests a lack of focus.

There have been reasons both mitigating (injuries) and galling (boredom), but the bottom line is that the Celtics are not a very good basketball team right now and they haven’t been since the calendar flipped to 2010.

The Celtics continue to insist that the problems lie entirely within them and that they possess the power to address them. 

“We know the issues,” Rivers said. “It’s not anything we don’t know. We’re just not doing them very well and we’ve got to keep working on them. There is nothing wrong except we have to keep working to get it right.

Pressed further, Rivers continued: “I would like it not to [happen], but this is basketball and it happens. We’re not used to it happening here, but it happens. I’m not going to overreact to it, I can tell you that. Sometimes you can see it on the film, sometimes you can see it on the floor. Sometimes you’ve got to get your butt whipped a couple of times before you can see that it’s a problem. I’m hoping all those things will help us.”

It may not be that simple, however.

THE DANGEROUS GAME OF TURN IT ON/TURN IT OFF

Let’s assume for the sake of argument that the Celtics are merely biding their time until the playoffs start. There is an enduring myth throughout the NBA that veteran teams have a mystical ability to flip a switch and get it right in time for the playoffs. The team that is referenced most in that discussion is the 2006-07 Spurs.

That team won 58 games and finished a distant second to the 67-win Mavericks in the standings. From late December to mid-February, the Spurs turned in a pedestrian 13-12 record amid calls that they were too old and that management should blow up the team.

Sound familiar?

It’s a tempting analogy because in many ways the Celtics are the Eastern Conference version of the Spurs. They are a veteran-laden, defensive-oriented team built around a Hall of Famer anchoring the backline.

Emerging point guard Rajon Rondo has often been compared with Tony Parker, both because of their suspect outside shooting and their blazing speed. Rivers even spent time on the sidelines as an assistant under Gregg Poppovich, and he has modeled a lot of his team’s approach on that of the Spurs. 

Tempting yes, but the difference is that despite the surface similarities, the Spurs responded to their midseason funk by winning 13 straight games and going on a 25-3 run down the stretch.

They also had the best point-differential in the league, and their future Hall of Fame center, Tim Duncan, was still playing like a Hall of Fame center.

Perhaps the Spurs did drop down a gear during the 82-game grind and then turn it on in time to capture their fourth championship of the Duncan era. But that team also was blessed with solid health, good depth and three players — Duncan, Parker and the forever-underrated Manu Ginobli — having All-Star-caliber seasons. 

The Celtics have not been healthy, which has decimated their depth, and while they did have three All-Stars, it’s hard to make the case that they’ve had three All-Star-caliber players.

The Celtics may have turned it off, but until they prove that they can turn it on like that Spurs team, their approach remains suspect. To put it another way, there’s a reason why the Spurs are the exception and not the rule.

THE INJURY FACTOR

In terms of games missed, the Celtics starters actually have been fairly durable. Ray Allen, Kendrick Perkins and Rondo have missed only two games between them, although Perkins seems doubtful for Tuesday’s game with the flu.

Pierce and Kevin Garnett have missed 21 games between them, which isn’t insignificant, but it is right in line with the other contenders.

Denver’s Carmelo Anthony and Chauncey Billups have been out 22 games because of injuries, as have the Lakers’ Pau Gasol and Kobe Bryant. With the exception of the Hawks, who have had only one game missed by a starter, all the top contenders have had some health-related problems.

Kevin Pelton of Basketball Prospectus did the injury research and noted that the Celtics have struggled without Paul Pierce even more than they have when they were without Kevin Garnett. Pierce has not been right since hurting his foot against the Wizards on Feb. 1.

To its credit, the team has not used injuries as an excuse for its problems.

“This is not three or four years ago when I sat [and] we had no chance of winning,” Pierce said Monday. “We have a team that we should win. We’ve won when Kevin sits out. We should win when I sit out, if Ray happens to sit out. These are games, the last couple that we should have won. There’s no excuses.”

No, injuries aren’t an excuse for failing to do the little things that are necessary to win basketball games, but they are a factor.

The starting five has only played together 11 times since Dec. 22 and the Celtics' record is just 6-5 in those games, suggesting that even when they have all played, they haven’t been at full strength. Beyond the starters, Marquis Daniels and Glen Davis have been out 56 games between them, which is a huge chunk of the rotation.

At this point, it seems fair to question if the Celtics are ever going to be healthy enough to make it through the rigors of the regular season, let alone the playoffs. If that’s the case, then no amount of soul-searching or attitude adjustment can help them.

MARCH MADNESS

There is some light to be found at the end of the dark tunnel, and it’s staring them right in the face, but it comes with an important caveat.

The next 10 games offer a good news/bad news proposition for the Celtics. The good news is that nine of their next 10 are against teams who are either .500 or way below (with Cleveland thrown in for good measure). The bad news is that they will all take place in the span of 16 days.

The good news is that six of those 10 are at home. The bad news is that the Celtics have a 16-11 record at TD Garden, which ranks 18th among NBA teams and is in a virtual tie with the Clippers for that distinction.

“It is troubling,” Rivers acknowledged of the team’s mark in Boston. “Of all the things to me, even with the rebounding, is how we’ve performed at home. The one thing that’s bothered me more than anything has been that. I don’t care what your injuries are. You should win at home.”

Rivers also noted that despite everything, the Celtics still are within a game of the second seed in the Eastern Conference.

That’s true, but with 17 games in 31 days, the month of March should have been about the Celtics resting up and fattening their record on the NBA’s vast middle class. Instead, it has turned into a nightly survival test.

“It’s 48 minutes of concentration,” Pierce said. “Forty-eight minutes of playing through the game. We’ve been doing this for the last couple of weeks, not running through the race. You’ve got to finish the race, and that’s what it’s all about.” 

They have talked about being bored with the process and growing restless waiting for the playoffs to begin. Now with 25 games remaining, the playoffs are within sight and they have work to do.

If they are right and their problems are their own, and not because of injury or age or erosion of talent, then they have no one to blame for being in this position but themselves. But they do have to put in the work.

The next 10 games should tell us a lot about the Celtics, but maybe we already know everything we need to know.