Just as the Celtics were trying to lock up the third seed in the competitive Eastern Conference, they slipped. They have dropped down to fifth following a mediocre 8-7 stretch since the All-Star break, now finding themselves just four games clear of the playoff line.
Boston has been an advanced-statistics darling, putting up the eighth-best net rating in the league. Since the break, however, the Celtics have outscored their opponents by just 0.6 points per 100 possessions, a considerable 2.6-point drop from their season average.
There are several issues causing this slump, and the Celtics must address them now if they want to make some noise in April and beyond.
The Celtics have done admirably well without a top-20 player on the roster, as head coach Brad Stevens has utilized a strength-in-numbers approach. Boston has adopted a selfless, ball-sharing offense, expertly pivoting around the notion that a top team needs to have a superstar.
Isaiah Thomas has filled the shoes of go-to scorer, but he isn't necessarily a player who can reliably draw help defenders down the stretch of games. Opponents often throw their best defender his way and are content with other Celtics making a big play.
The lack of another truly explosive scorer has manifested itself through inconsistency. It's something Boston has struggled with often, especially early in the year. The Celtics would look worthy of true title contender status on one possession, only to crumble and appear lost in the next.
Those blips seemed momentarily fixed when Boston put together a 12-3 stretch starting in mid-January, including a promising 14-game winning streak at home. The team's form has been shaky since then, with five losses in the last seven contests.
The Celtics are morphing into a different team from quarter to quarter. That was especially evident in the 105-91 loss to the Toronto Raptors on Friday. Boston was sloppy out of the gate, surged in the third period to cut the lead down to five and then let go of the gas pedal again. Stevens tried to salvage a positive element from the game, but he only echoed the issue.
"I thought we played the best in the third quarter that we’ve played in two weeks, so that’s good," Stevens said, per ESPN.com. "We have to sustain it for a longer period than one quarter."
Boston has shown that it can remain focused and close out games with discipline and poise earlier this season. Using the lack of a superstar as an excuse is lazy, and the recent shaky play stems from several other problems which require attention.
The Celtics offense has evolved since the beginning of the season, and every individual has bought into the concept of unselfish basketball. But Boston's true backbone has been its suffocating defense, which for a while trailed just the San Antonio Spurs.
Since the All-Star break, Boston has surrendered 104.9 points per 100 possessions, which would be tied for 19th in the league over the course of the entire season. Due to this slump, Boston has slipped down to fifth in defensive efficiency.
Stevens is well-aware of the issue, and admitted that it's not just a cold stretch, according to Jay King of MassLive.com:
It's not realistic to not have (slippage) at times through 82 games. But it's very concerning when it's the better part of three or four weeks. There's a lot of teams that have had slippage at this time of year especially, but we said this before, we severely limit our margin of error if we don't defend at a high level.
In the past we really hurt ourselves because we didn't score it at all. Now we're scoring it well but it's still not good enough to win consistently at the level we've defended in the last three weeks or so.
Some of the Celtics' issues don't have an easy fix. The team still lacks a true rim protector, although Amir Johnson provides a small dose of that. Whenever Boston fields a versatile and mobile lineup that can switch pick-and-rolls, it becomes vulnerable at the rim.
The Celtics have also been exposed against teams with length. With Jae Crowder out, Stevens opted to start with three guards in last Wednesday's 130-109 loss to the Oklahoma City Thunder. Kevin Durant peeled off three straight baskets against Marcus Smart to start the game, including this post-up:
Part of the problem may have been a schematic flaw—Smart, as great of a defender as he is, should never have to defend Durant one-on-one—but it's also a lack of urgency on the team's part. It took way too long for Jared Sullinger to help, and the Celtics have regularly been caught napping like this.
Boston's backcourt players may be feisty, but the team has to be more engaged and work on help coverage to make up for the lack of size.
Boston's collective energy has been underwhelming lately, but the recent slump also has a lot to do with injuries.
The Celtics can be a formidable opponent in the playoffs, but they need to have every single player available. As soon as a starter or key bench cog drops out of the rotation, Boston struggles to fill the gap, despite having a lot of depth on paper.
Crowder's recent absence due to a high ankle sprain has highlighted just how vital the versatile wing is. With him sidelined, Boston loses an essential slasher, three-point threat and pace in transition. Even though he isn't a natural playmaker, his aggressive dives to the rim open up possibilities on the perimeter.
Crowder's defensive versatility is also a missing component, as no Celtic is capable of guarding as many positions as he can. Without him, Stevens' three-guard lineups are considerably more vulnerable and often overwhelmed by opponents with length.
Kelly Olynyk's 12-game absence was also a heavy burden, especially in the floor-spacing department. Boston has been one of the five worst shooting teams since the All-Star break, connecting on just 32.2 percent of its three-point attempts. The Celtics are also taking two fewer long-range shots than their season average in that stretch.
Olynyk is back in the lineup, but he still needs to shake off the rust. Crowder, who was supposed to miss at least another week of action, appears to be ahead of schedule, according to King. The Celtics should still take a cautious approach, even with a tough five-game road trip looming and playoff seeding in jeopardy.
It's impossible to control injuries, but the team can dictate the recovery process. Sacrificing a couple of wins in order to be fresh for the postseason shouldn't be a dilemma at this point.
All statistics courtesy of NBA.com and are accurate as of Monday.