Optimists could certainly point to Boston's late run last season as evidence that it's never too late for a turnaround. When the Celtics snapped out of their funk at the 2011-12 All-Star break, they rode the momentum all the way to a Game 7 against the Miami Heat in the Eastern Conference Finals.
Momentum really is a key term to use when describing last year's Celtics.
Over the final three months of last season, Boston's differential (the margin between the points it scored and allowed per 100 possessions) trended consistently upward. From less than a point per 100 possessions in February, the Celtics' improved to 2.7 in March and rose all the way to plus-6.4 in April.
As the 2011-12 season wound down, the Celtics were ratcheting things up.
Contrast that story with the one playing out right now and the differences hit you in the face like an errant (but also possibly intentional) KG elbow.
The 2012-13 Celtics enjoyed a respectable plus-4.8 points per 100 possessions advantage in the month of February, but have since seen their differential fall to just over a half-point per 100 possessions in March.
Tossing out figures like this might seem like a reductive way to convey the more complicated story of the Celtics' recent decline, but it's critical to note that there really is a key difference in the team's year-over-year trajectory. The broad numbers reflect that difference.
And in fact, the similarities are discouraging, too.
The Celtics haven't been a good rebounding team in either of the past two seasons. They pulled down about 47 percent of all available rebounds last year, which is pretty much what they've done over the past month of this season. Anything under 50 percent is quite obviously bad, as it means that the team is being out-rebounded, but 47 percent is practically crippling.
Because the Celtics played such phenomenal defense last year, their poor rebound rates and pedestrian offensive production didn't ultimately slow down the team's stretch run.
But things are different this time around.
Chief among those differences is the absence of Garnett from the lineup. With KG sidelined because of an ankle injury, Boston is going to have to feature Jeff Green and Brandon Bass more often up front. Anyone who has watched the Celtics play this season knows that Green and Bass haven't exactly been a defensively dynamic duo.
According to Grantland's Zach Lowe:
The Celtics have allowed 106.6 points per 100 possessions when [Green and Bass have] shared the floor, per NBA.com. That would rank 25th overall for the season, which is a problem, since the Celtics as a team have actually allowed 99.8 points per 100 possessions—the sixth-stingiest mark in the league.
So, with a five-game losing streak in place and an almost certain defensive downturn coming, the Celtics are in danger of heading into the postseason in a form that doesn't remotely resemble the team that made noise last year.
Without an elite defense to help cover up a merely passable offense, this year's Celtics are coming down the stretch with no real identity on which to hang their hats. The team certainly isn't going to be defined by its stopping power without Garnett on the floor—Boston allows seven more points per 100 possessions when he sits—and nobody's going to mistake it for an offensive juggernaut, either.
The Celtics are nearly mathematical locks to make the postseason, so there are no potential lottery concerns here. But there is a very good chance that they'll slip into the undesirable eighth spot. More than that, there's also got to be a more pervasive, scarier feeling bubbling up around the Celtics.
Not only are they running out of time to start looking like a playoff team, but the Celtics appear very much like a team whose window is almost shut for good.