The Boston Celtics greatest strength is their depth on the wing. Jayson Tatum, Jaylen Brown, Gordon Hayward, and Marcus Smart all spend time sliding through the 2-4 spots. None is quite like the other, but each is long and athletic, and capable of making a positive impact on both ends of the court. Boston’s relative advantage in this regard is immense.
Teams dream of employing just a single multi-positional defender who can dribble, pass, and shoot. Boston has a cadre of them. Having an All-Star point guard in Kemba Walker in the mix doesn’t hurt either.
The Celtics’ options at the big position aren’t quite so sexy. They’ve found a reliable starting center in Daniel Theis after the departures of Al Horford and Aron Baynes from last season. He’s a tad undersized and somewhat lacking in explosiveness, but he makes up for those deficiencies with intelligence and expert timing. Theis can bang with most bigs on the block sufficiently enough for his rangy teammates to dig down on the ball or bring a hard double.
Force him to defend in space in the pick-and-roll, and Theis is more than capable. He leverages his instincts and surprisingly nimble feet to position himself between both the roll man and attacking ball handlers.
He’s agile enough to defend switches against smaller players as well.
Theis has been something of a revelation for Boston, but he isn’t a panacea. The lithe german big man has averaged just 23.8 minutes per game this year, leaving roughly half the game’s center minutes to alternative options. That’s a lot of time for the Celtics rotational bigs to fill, particularly if the team wants to allot power forward minutes to non-wings and play any of its backup big men together or alongside Theis.
Boston has pieced things together nicely enough to date, and will likely continue to do so heading into the postseason, but the question of whether or not the Celtics’ platoon system can stand up to the rigors of the playoffs looms large.
Head coach Brad Stevens has a wide variety of player types at his disposal. Enes Kanter is his most seasoned and sizeable option. Kanter is an excellent rebounder and an offensive fulcrum for second units. He mushes smaller opponents below the hoop, battering his way to simple hook shots and trips to the free throw line.
Defensively things are far less pretty. Kanter tries hard, but he’s a disaster defending the pick-and-roll. Opponents scoot right past him for easy finishes by the basket and kickouts to open three-point shooters when the Celtics scramble to erase his mistakes.
Boston can rely on Kanter to stand stout one-on-one in the post - which makes him an interesting option in attempting to solve the riddle that is Joel Embiid - but any team with even decent pick-and-roll ball handling can turn him into a major liability defensively. Those types of players tend to get played off the court as the postseason progresses.
In instances where Kanter’s inability to defend in space are too damaging, the Celtics have at times turned to Grant Williams. Boston’s barrel-chested rookie is the inverse of Kanter, undersized, preternaturally instinctive as a defender, but a near non-entity on offense.
Williams has excellent timing defensively. He moves his feet well enough to defend on switches, and always knows where he and his teammates are supposed to be. Williams isn’t quite long enough to be an elite rim protector, but he gladly throws his sturdy frame in front of oncoming traffic, and does so far enough from the hoop to be a real impediment.
Offensively Williams is decidedly timid. He sports a miniscule 11.0% usage rate per Cleaning the Glass. In theory, he’s an effective post player, but the Celtics have been very hesitant to attempt to get him any mismatches in the post. Williams is a monster screen setter, which brings some value on the offensive end of the court, but ultimately whether or not he can be a postseason rotation piece will come down to his shooting.
Williams’ three-point percentage hovers at a disastrous 24.7%. Optimists will point to an 0-for-25 streak to start his career that has skewed the data, suggesting that his improved marksmanship since that point is a better indicator of his real ability. Williams isn’t precluded from growing as a shooter over the course of the year, but this line of thinking is dangerous. The fact that he missed so many consecutive shots has to be accounted for in the assessment of his ability to knock down open looks from deep.
Opponents treat him as a non-threat, and that means they can leave him alone on the perimeter to muck up the rest of Boston’s offensive efforts. If Williams can’t consistently splash home triples, he too runs the risk of being played off the court against the league’s upper crust in the bubble.
Enter the Celtics theoretical solution, Robert Williams III, an exceptional athlete with a clear cut set of skills that can be applied both offensively and defensively. Williams is a freakish leaper with an impressive ability to catch lobs thrown at all varieties of angles. He gives Boston an element of vertical spacing that none of the team’s other bigs can provide.
Pressure on the rim leads to rotating defenders and more room for attacking off the bounce, two things the Celtics have the perimeter options to prey on mercilessly.
Defensively, Williams’ athleticism is again the key to his utility. He pops off the floor for fantastic blocked shots, and has enough quickness and explosion to make up for most of the mistakes he makes defending smaller opponents on switches.
Unfortunately for the Celtics, Williams exists almost exclusively in the theory. He’s been injured for the majority of his career, and the minutes he has played - while marked by flashes of special talent - have been checkered with mental mistakes. Williams needs a lot more reps before Boston can trust him to be in the right positions defensively or to function as a reliable decision maker on offense. The postseason probably isn’t the right time to practice those things.
That doesn’t mean Williams won’t see any action. Stevens doesn’t need all his backup bigs to achieve full NBA self-actualization in the playoffs. They just need to do enough collectively not to sink the ship, while their star-level teammates on the perimeter do the heavy lifting. That will likely mean a lot of matchup-dependent mixing and matching.
The Celtics have a selection of backup bigs with a breadth of skills, but for all their varied talent, each available option also has at least one potentially fatal flaw. The NBA Playoffs are unkind to players that have holes in their games. To win at the highest level, Boston will either need to juggle its rotation just perfectly enough to hide the deficiencies possessed by their rotation big men, lean into a super small ball identity, or cash in on some unexpected growth over the course of the postseason.