With just over six minutes to play on Christmas Day, Kyrie Irving sent the TD Garden into a frenzy with a 3-pointer that put the Boston Celtics up 95-90 on the Washington Wizards.

That, though, was the last big cheer the Celtics would get. After Irving's 3, the Celtics were outscored 21-8, as they collapsed down the stretch, unable to get a rebound (they literally didn't get a defensive rebound over the final 6:56), or enough stops to slow down the Wizards.

It was the fifth loss in the last 10 games for the Celtics, who have fallen just five times in their first 27 games this season. After starting out 22-5 and looking like the class of the league, they're now 27-10. So what's up with the Celtics, and should there be concern?

Victims of their own success

First of all, 27-10 is a great record to have almost halfway through the season. If the Celtics had this record with Gordon Hayward, there really wouldn't be too many complaints, and the fact that they've won this much without him is quite impressive.

The "problem" for the Celtics, is that they started off so incredibly hot with that 16-game winning streak early in the season. That, along with doing things like making an 18-point comeback to beat the Warriors, elevated their expectations for what they could accomplish this season without Hayward. They're a very solid team, and still one of the East's best, but they aren't the world beaters they looked like early on.

Also, if they had gotten to 27-10 with the help of a couple five- or six-game winning streaks, and built the record up gradually over the season instead of all at once, it wouldn't look as bad when they go through an average stretch.

The schedule

Boston's sheer amount of games, coupled with the fact that so many of them have been over the past few weeks, is clearly taking a toll on the team. Not only has its record suffered, but so too have the players. Jaylen Brown, in particular, has been dealing with Achilles soreness that was caused by overload from the schedule, and he just came up hobbled again on Christmas, leaving the arena on a crutch -- though that injury seems to be a sprained ankle.

The Celtics have already played 37 games this season, while nearly a third of the league has played just 32 games or less. The Phoenix Suns (35 games) are the only other team in the league who's played more than 34. December, though, with 17 games on the docket, has been particularly brutal for the C's. It's no surprise that their recent slide coincided with a hellish stretch of eight games in 12 days that included three back-to-backs. 

There is some good news on the horizon for the Celtics, however. In early January, they will travel to London to take on the Philadelphia 76ers, and on each side of that game, they'll have five days off, which should provide some much-needed rest. 

Rebounding

Last season's Celtics team was beset by rebounding problems, as Robin Lopez exposed in their first-round playoff series against the Bulls. But with nearly a completely new roster this season, that problem seemed to have been solved. The Celtics were quite strong on the boards for the first few months of the season, recording a rebound rate of 51.6 percent (eighth in the league) prior to this recent 10-game stretch.

Over the last 10 games, however, when the schedule has really seemed to start affecting the team, the rebounding has fallen off a cliff. They've grabbed just 46.7 percent of available rebounds in the last 10 games, which is 28th in the league over that span.

With rebounding being largely about effort and energy, it follows that the Celtics would suffer in that area given the workload they've put in over the past few weeks.

Defense

The Celtics have been one of the league's best defensive teams this season, and even after the loss to the Wizards, they're second in the league in defensive rating, giving up just 101 points per 100 possessions.

That, though, is a testament to how strong they were early in the season, not to what they've done lately. Prior to this recent 5-5 stretch, the Celtics were the best defense in the league, boasting a stout defensive rating of just 99. Over the last 10 games, however, they've been giving up 105.4 points per 100 possessions, which is 16th in the league during that span.

And their lack of rebounding is a big component of this. Holding opponents to just one shot is a huge part of having a strong defense. The more chances you give your opponent to score, the more they're going to do just that, because your defense gets worn down when you have to try and stop a team two or three times on the same trip down the floor.

Playing middle-of-the-road defense isn't the worst thing in the world, but it greatly lowers your margin for error -- as was evident over the last half of the fourth quarter against the Wizards.

All of these factors have been building on each other, and now it seems as though there's a crisis for the Celtics or something. But here's the thing: there isn't one. 

The Celtics are a good team. They aren't going to run through the league like they did on their 16-game winning streak, but they're good, even without Hayward. The regression from that winning streak was always coming, and right now it's just being exacerbated by this packed December schedule, which has taken a toll on the team, especially on the glass and on the defensive end. 

This recent .500 stretch isn't surprising, and it probably isn't a big deal. Once they get through December and can get a few days off, some practices and a more conventional schedule, the Celtics will look more like the team they were early in the season than the one that's been sputtering as of late.