Robert Williams is massively important to the Boston Celtics, especially on the defensive end. This is obvious. There are a bunch of stats out there that prove how much better the Celtics are with him out there, like how Boston is holding opponents to more than eight fewer points per 100 possessions with Williams on the floor in the playoffs.
There are also a bunch of plays that I can show you to illustrate his impact on the defense.
But instead, I’m only going to show you one:
At first glance, it’s a nice defensive play. Williams picks up Jimmy Butler, hangs with him all the way to the rim, and blocks his shot. Great play.
But there's so much more to this that really shows you how much of a difference he makes. In a sense, He’s defending everyone on the floor in this play, just by what he’s able to do with Butler.
Let’s start with the set up.
Williams is switched onto Butler (he started on PJ Tucker), and Butler goes from the corner to the right wing.
When you watch the play all the way through, notice that Williams breaks for Butler before Kyle Lowry even gets the ball. So the first reason why he’s so good defensively is recognition of the play. He knows the ball is swinging before the ball is in Lowry’s hands.
The second reason is that he’s under complete control in his close out. He goes from the right block to the right win but doesn’t fly past Butler. He doesn’t anticipate a shot and run out off-balance. Butler senses the closeout, but because Williams is under control, he can hang with Butler on the drive.
Pay attention to the help defenders on that left side. Al Horford on Bam Adebayo, Jayson Tatum on Tucker, and Jaylen Brown on Lowry.
Williams stays with Butler on the drive, but the help defenders barely move. The third reason why Williams is this important is that he can guard a wing driving from the perimeter and everyone else can stay home. Derrick White can stay face-guarding Max Strus. Brown is the only guy who takes a slight step towards Butler. Both Horford and Tatum actually move closer to their guys.
This is the opposite of what’s supposed to happen during a paint touch. Paint touches collapse the defense. When Butler gets into the paint against other defenders, he requires a bit more help. Against Williams, not so much.
This takes away all of his drive and kick options as well as a dump off or lob option to Adebayo. By the time Butler is in the restricted area, Horford’s toe is actually out of the lane as he makes sure Adebayo is not an option.
The fourth reason for Williams’ defensive excellence, which earned him a spot on the NBA’s All-Defensive team, is his athletic ability.
Butler is in the restricted area and he uses his shoulder to clear some space to knock Williams back. Butler then leaves his feet to take the shot well before Williams leaves his.
But Williams is so gifted athletically that he’s able to recover and block the shot even after Butler is in the air.
Granted, Butler may have been limited by his right knee but Williams has been limited by his left knee, so they’re at least a little bit more even there. Regardless, Williams doesn’t have to bit on the fakes or tricks that Butler likes to use to get to the line. His athleticism allows him to wait on drivers and shooters to commit to the jumper before he challenges the shot.
Being able to single cover a Miami drive and not give them outlets to open shooters helps drive an already iffy half court offense deeper into the dirt. If Boston is scoring on the other end (aided by Williams’ offensive rebounding ability) and setting their defense, Williams alone can increase the effectiveness of an already tough Celtics defense.