Paul Pierce was frustrated. He wasn't alone. All of the Celtics shared the captain's sentiments after getting shut out for the final 4 1/2 minutes and blowing a winnable game on their home floor against the upstart Cavaliers. There were explanations -- too many turnovers, too much Kyrie Irving and Anderson Varejao -- but the realities were offset by the crushing nature of the 88-87 defeat.

“This loss hurt. Let’s not sugarcoat it, this one hurt,” Kevin Garnett said. “There’s all types of sprinkles on top of this cupcake. It hurt. I don’t know a guy in here that wasn’t very, very distraught and upset today.” 

The Celtics were on the brink of winning their fifth straight game and climbing back over the .500 mark for the first time since they were 4-3 to start the season. Ray Allen returned from an ankle injury and looked like his old self, dropping 22 points on just 14 shots and making four of his six 3-pointers.

They had survived his absence, as well as Rajon Rondo’s, and were beginning to look like the team that everyone has known and the league has feared these last 4 1/2 seasons. And then, things fell apart.

The Celtics couldn’t score. They couldn’t stop Irving from penetrating at will on the pick and roll, and when the rookie did miss, which wasn’t often, Varejao was there to clean up the mess.

“Defensively, I thought we were solid throughout the game, but in that fourth quarter on the ball in pick and rolls we reverted where we didn’t take the ball out of Kyrie’s hands,” Allen said. “At least make him see more pressure and make him play under duress. He got to his spots and made the plays he needed to make for his team, and I don’t think at any time we recognized that.”

And offensively? “I missed a layup. I had a good look at a 3. We had those looks,” Allen said. “With the lead that we had, if we made stops it wouldn’t have mattered.”

Which brings us back to Pierce, who sat for the first eight minutes and 18 seconds of the fourth quarter. The Celtics began play with an eight-point lead. It shrank to three, but the reserve players pushed it back to double digits. The Cavs didn’t go away, and that’s when Doc Rivers put Pierce and Garnett back in the game.

“Maybe I should play a little bit more,” Pierce said when asked about the fourth-quarter difficulties.

Asked if Rivers talked to him about his substitution pattern, Pierce said, “That’s not his job to explain that. The coaches make their decisions, but at the time we had a pretty good lead. I can understand it.”

Still, Pierce added, “I don’t think this would have been the outcome, though. I’m more upset with losing, more so than not getting back in there. I would have liked to have been there to finish off the game. At the time you can understand when we have an eight-point lead to rest the guys, so it’s a double-edged sword.”

It was an interesting call for Rivers. If the Celtics had succeeded in pushing the lead back up to double digits, Pierce and Garnett could have been afforded the extra rest. It stayed at eight and the coach made his move.

“You can see that they were gaining some momentum, but I trust Doc in any decision that he makes,” Garnett said. “As players, it’s for us to finish games off and execute game plans and such. As players, we have to do our jobs and finish it, and we didn’t do that. Lesson learned.”

“It was tricky,” Allen added. “There was a point where I came back in, it was a three-point lead and we stretched it. There was an idea in my mind that at some point if we keep stretching this then Kevin and Paul can rest on the bench. It’s a fine line. You’re looking at the clock and by that time they’ve gained momentum and now you’ve got to put Paul back in and it’s a little too late.”

There’s a good chance that all of this will be nothing more than a mild tempest for the Celtics -- some in-flight turbulence on their journey back to respectability. Pierce and Rivers have been through far tougher times together than one regular-season game in January for this to linger.

But Rivers is walking a tightrope this season. His players came in out of shape and not ready to play the season. They struggled through some of the bleakest times in the Big Three era, which set the early tone for this season.

The Celtics aren’t going to challenge Miami or Chicago for homecourt advantage and they are in danger of falling too far behind Philadelphia to make a run at keeping hold of the Atlantic Division. The idea is to get to May in one piece, avoid the Heat or Bulls in the first round and make one more stand before the inevitable franchise restructuring takes place.

Rivers’ job is to win games and make sure his team is still standing at the finish line, and the two things are sometimes mutually exclusive. His starters have already missed 17 games because of injuries and he’s tried to keep his veterans’ minutes down to an acceptable level despite a shaky bench that is still finding itself. At the same time, the Cavs may have stayed in the game against the second unit, but they won it against the starters. The rematch is Tuesday in Cleveland.

“They beat us on our floor and we have to protect what we have here better than what we’ve done,” Allen said. “We’re all kicking ourselves. Everybody’s really pissed that we let this game slide. I’m glad it’s not football where you've got to wait a week. We’ve got to turn right around and do it and be ready.”