The Boston Celtics will be without Marcus Smart when they tip off their second round series against the Milwaukee Bucks on Sunday. The rugged guard/wing/forward is sidelined by a partially torn oblique muscle. It’s not hard to deduce that Boston would prefer to have Smart in the fold. He’s one of the league’s best defensive players and the Celtics’ emotional heartbeat.

They’ll certainly miss him, but the NBA Playoffs demand a more nuanced understanding of the ways in which Smart’s absence will impact Boston’s performance than simply stating it’s not ideal. So we’ve taken the time to break things down into different domains of the game, assessing the degree to which Smart will be missed in each.

We’ll start on the defensive end, as that’s where Smart has the greatest influence.

On-Ball Defense

Smart is an absolute pest defending on the ball - and anywhere really - he’s incredibly strong, quick enough to slide with just about anyone, and dogged to a degree that allows him to make up almost any athletic advantage an opponent might have. Toss in a pair of quick hands, length to cover multiple perimeter positions, and a willingness to flop shamelessly, and you’ve got a perfect recipe for ruining people’s days.

But Milwaukee doesn’t necessarily require that player. Giannis Antetokounmpo is one of the few players in the league with enough strength and length that it doesn’t make sense to match Smart up against as a primary defender. His prowess on the ball could be useful against Khris Middleton - who killed the Celtics with some truly impressive shotmaking last year - or Malcolm Brogdon, should he return from injury, but the most important defensive task is dealing with Antetokounmpo when he has the ball in his hands, and Smart wouldn’t be functioning as the first line of defense against him all that frequently.

Degree to which Smart will be missed: Significantly, but not cripplingly.

Off-Ball Defense

Woe unto those who try to set a screen on Smart away from the ball. He’s a crazy person, and a damn strong one. If he can’t quite slither around a pick, he’s going right through you. The Bucks have plenty of players capable of knocking in open looks, but they don’t have many shooters that can hit shots off balance or with the smallest amount of daylight (think Klay Thompson or J.J. Redick). That means Smart’s absence won’t be felt quite as intensely as in other arenas.

Jaylen Brown can handle the toughest off-ball duties just fine, assuming he can stay locked in. The playoffs seem to help him in that regard.

Degree to which Smart will be missed: Not all that much.

Help Defense

Smart’s intelligence makes him a menace as a helper. He’s an expert jumping passing lanes, and a shockingly impactful deterrent at the rim given his height and tendency to be matched up with perimeter players. Missing Smart as a helper is probably where the Celtics will suffer the most. Stopping Antetokounmpo without getting buried under a barrage of open three-pointers from his supporting cast requires perfectly executed help.

It also demands a certain degree of psychotic competitiveness, given the frequency with which playing the “right” defense will end in failure and the sheer terror that Antetokounmpo’s athleticism rightfully instills in those sliding into his way. Smart has that in spades.

He loves sticking his nose where it doesn’t belong, and almost always does so with perfect timing. Boston will miss Smart dearly as it tries to muddy things up against Milwaukee’s beautiful offensive machine.

Degree to which Smart will be missed: A ton.

Shooting

Smart improved substantially as a shooter this year, hitting on 36.4% of his looks from beyond the arc. That may not sound all that impressive, but he was arguably the worst shooter in the history of the NBA, as compared to his volume, across his three previous seasons. That never kept him from chucking.

Smart’s willingness to take open shots won’t be missed much against the Bucks, even with his newfound league-average stroke. That’s not to say that he shouldn’t hoist a few triples when he’s on the court. There is value to shooting when you’re open. It forces defenses to think in a way that complete non-threats (looking at you Ben Simmons) simply can’t. Taken in the aggregate the potential detrimental effects of Smart being an at best average shooter are far outweighed by the positives he brings elsewhere.

But for the purposes of this exercise, in which we are specifically evaluating the way in which Smart’s absence will impact this specific component of Boston’s collective effort, the Celtics may find some benefit in having to play others. Gordon Hayward, Jaylen Brown, and Jayson Tatum project to eat up the majority of the minutes that Smart’s injury leave available. All of whom are far more effective shooters.

Degree to which Smart will be missed: Not at all.

Ball Handling/Playmaking

Smart isn’t a particularly dynamic threat with the ball in his hands. He’s not a real threat to blow past anyone for easy buckets at the rim, nor anything approximating a pull-up artist from anywhere on the floor. But he’s crafty in the pick-and-roll and a very good passer. Putting the ball in Smart’s hands lets Boston play around with Kyrie Irving and Terry Rozier as off-ball threats, enabling the former to create chaos in a brand new fashion and the latter to not have to try to do more than he’s capable of offensively.

Smart would be hugely valuable as a ball handler should Milwaukee opt to stick to its typical defensive strategy. The Bucks are ultra aggressive in defending the rim, and often surrender oodles of open three-point looks for bigs and wings as a result. The Celtics could leverage that reality to get Irving great catch and shoot opportunities by having Smart initiate the offense, and placing Irving in a position where they know rotations are liable to break down.

Milwaukee wouldn’t stand for Irving raining in open shots for long. The Bucks would be forced to switch their strategy in such a scenario, and in that sense Smart’s value in this particular domain is likely more theoretical than practical. Having a steady hand to slow things down in high-pressure moments would be useful regardless.

Degree to which Smart will be missed: Depends on strategy, but probably just a little.

Heart

Hustle, heart, grit, determination - pick any coach’s cliche. Marcus Smart embodies it. He’s all over the court all the time. Ball on the floor? Smart is diving head first for it. Massive human barreling down the lane? He’s stepping in to take a charge. Need a big rebound on either end of the court? Smart is climbing into the trees and grabbing it or taking it away from whoever else gets it.

Boston needs every edge it can get against Milwaukee, and they’re losing one in the competitive insanity that Smart brings to the team. It’s hard to quantify just what kind of impact intangibles have on a team, but if you’ve ever watched Smart play in the playoffs then you know its not nothing.

Degree to which Smart will be missed: As much as is humanly possible.

It’s worth mentioning that none of the areas of the game of basketball outlined above actually happen in a vacuum. There is value in digging in deep on the specific impacts of Smart’s absence, but at the end of the day his influence on the game is an amalgamation of all of the above. There are moments throughout the series where his combination of skills would be more valuable than others, and the Celtics will be frustrated not to be able to turn to him.

The postseason requires game-to-game and even play-to-play adjustments which are most easily made when a team has its full compliment of players. Smart’s injury limits the realm of possibilities that Brad Stevens can explore tactically. Or at least it does for now.