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The Celtics’ greatest weakness is their rivals’ greatest strength

The Celtics’ defense has been outstanding everywhere outside of the post. Post-ups are typically inefficient shots, so is it worth being concerned about a poor match up against the 76ers?

NBA: Philadelphia 76ers at Boston Celtics Greg M. Cooper-USA TODAY Sports

Rick Carlisle is done hearing about post ups. From his post-game press conference on December 26th:

“The post up just isn’t a good play anymore. It just isn’t a good play. It’s not a good play for a 7’3” guy. It’s a low value situation. Our numbers are very substantial when he spaces beyond the 3-point line, you know, we’re a historically good offensive team. And when any of our guys go in there, our effectiveness is diminished exponentially.”

Carlisle is not alone in thinking post ups aren’t worth prioritizing. Here’s Mike D’Antoni’s brother Dan (yes, Dan D’Antoni) with one of my favorite explanations on how inefficient post ups are:

“If you can get a layup and it’s clean — it’s not one that’s highly contested — it’s 1.8 [points per attempt]. It’s 1.3 from the corner, 1.27. Do you know what a post up is with a guy standing over the top of you? It’s 0.78. So you run your team down there and see how long you can stay with teams that play the other way.”

Post ups are pretty widely recognized as one of the worst shots in basketball. If you’re focused on their proximity to the basket or the height of the player taking them, you’re stuck on the wrong details. Physical contact is off limits in most aspects today’s game, which accounts for some of the increased volume of three-pointers being taken. Post-ups are still pretty heavily contested, however, and some contact is allowed by referees, and even encouraged by fans. Why take the path of most resistance to score your points?

It’s no coincidence that the Celtics don’t chase post-dominant players in the most data-driven era of sports. In terms of scoring, they’re the second-most efficient in the league, but it only accounts for 3.8% of their offense - less than any other play type. Per Synergy, the Celtics are 29th in the league in defending them. Defending and scoring in the post is simply not part of the roster construction.

Boston Celtics v Philadelphia 76ers

This wouldn’t be of any concern if a division rival didn’t have one of the most post-dominant players in recent memory. More than 34% of Joel Embiid’s offense comes in the post, where he ranks in the 93rd percentile in efficiency. Think of it this way: Embiid has been almost as efficient on his post ups as Jaylen Brown has been on his spot up attempts. Jaylen, as you know, has been shooting the lights out. Embiid has been marginally less effective on vastly more difficult shot attempts.

What’s more impressive is that he’s doing it in greater volume, too. Embiid has 75 more post ups than Jaylen has spot ups, and is still keeping pace in efficiency even though he’s taking shots that are worth less points.

Can the Celtics afford to concede those points to Embiid and form a game plan around stopping other threats? I don’t know. Would you encourage other teams to simply let Jaylen shoot and try their hand and shutting down our other threats? You probably wouldn’t, right? And yet, we know beyond any shadow of a doubt that Embiid’s favorite shot is the single most inefficient shot in basketball. What do we make of this?

The 76ers have the 17th ranked offense, if we’re looking at points per possession. In a general sense, we know from our experiences watching the Celtics that having an average-at-best offense can be frustrating. But in more specific circumstances, such as a playoff setting, it can be crippling. And the circumstance here is the team with the second-best post up offense playing against the team with the second-worst post up defense. These two teams meeting in the playoffs is entirely within the realm of possibility.

It’s hard to tell purely through numbers how problematic this is for the Celtics. But we do have a pretty substantial body of evidence to suggest that the 76ers had no shot at beating the Celtics when they had two elite post defenders, and a much smaller body of evidence to suggest that they’re well equipped to beat them now that we don’t have even one proven post defender over 6’4” in height. And even then, Marcus Smart has only defended 32 post ups this season.

Enes Kanter has looked up to the task in two games against Philadelphia, but the numbers don’t support the idea that he can hold his own against Embiid. From my own article on the 21st:

“In 11 minutes and 53 seconds spent guarding him over the span of two games, Embiid is 7 of 18 from the field and 1 of 3 from deep. This accounts for 20 points on 18 field goal attempts, but doesn’t factor in five free throws on eight attempts. Overall, that’s 25 points on 18 field goal attempts in 12 minutes.”

We may never get a substantial look at our post defense outside of any game where our favorite team isn’t getting pummeled by Embiid, seeing as most teams don’t rely on post scoring as much as his team does.

I’m looking at a possible playoff series with the 76ers like a potential earth-bound meteor with an unclear trajectory. Do we simply cross our fingers and hope to avoid it? Do we start testing our missiles on other nearby meteors? Is that even a thing?

There’s no right or wrong answers here. I’d just rather not get hit by the meteor.

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