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Nylon Calculus: Why isn’t the Celtics offense working?

By Ian Levy

BOSTON, MA - OCTOBER 22: Gordon Hayward #20 and Kyrie Irving #11 of the Boston Celtics look on during a game against the Orlando Magic at TD Garden on October 22, 2018 in Boston, Massachusetts. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this photograph, User is consenting to the terms and conditions of the Getty Images License Agreement. (Photo by Adam Glanzman/Getty Images)
BOSTON, MA - OCTOBER 22: Gordon Hayward #20 and Kyrie Irving #11 of the Boston Celtics look on during a game against the Orlando Magic at TD Garden on October 22, 2018 in Boston, Massachusetts. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this photograph, User is consenting to the terms and conditions of the Getty Images License Agreement. (Photo by Adam Glanzman/Getty Images) /
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The Boston Celtics offense is clearly struggling. They’ve split their first two games, managing just 99.3 points per 100 possessions, second-worst in the league behind the Oklahoma City Thunder. Boston ranks no better than 14th in any of the offensive Four Factors, landing last in free-throw rate and 26th in effective field goal percentage.

The last number has been of particular concern — they ranked 15th last year and the thought (by me) was that a healthy Gordon Hayward and Kyrie Irving would add even more playmaking and shooting to a roster that already appeared loaded with both skills.

Four games is an extremely small sample, prone to swings of randomness and the question obviously becomes whether the Celtics are simply missing good shots or struggling to create them. Sam Sheehan of CelticsBlog wrestled with this very question and came away with the answer that it was probably a bit of both.

"As a matter of fact the Celtics are currently leading the league in both open and wide open shots. The gulf is particularly wide in the case of the “wide open” shots (6+ feet) where the Celtics have 103 and the second place Orlando Magic have 88. The shots are there, but the Celtics just aren’t finishing and executing."

Sheehan does a nice job of breaking down where the failures of execution are and the numbers definitely back up the argument that the problems are in both places. Daryl Blackport’s PBPStats.com features a measure of shot quality, expected effective field goal percentage, based on shot distance, angle from the basket, game and shot clock, quarter, score and the scenario that began the possession.

PBPStats estimates that the Celtics have been roughly average in shot quality, ranking 14th in expected effective field goal percentage at 51.0. Their mark thus far this season is identical to last year’s mark but last year they slightly overperformed, with an actual effective field goal percentage of 51.8 percent. This year, they’re underperforming significantly with an actual effective field goal percentage of 47.0 percent. Only two teams — the Thunder and Grizzlies — have underperformed their expected mark by a bigger margin so far this season.

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The granular numbers Sheehan highlighted fit the narrative as well — they’re second in the league in open field goal attempts and third in wide-open field goal attempts per game. However, they rank slightly lower in both categories if you filter to 3-pointers, which means a good number of the open shots they’re getting are inside the arc. They rank seventh in mid-range shot attempts per game and are one of just a handful of teams attempting more than 20 pull-up mid-range shots per game.

All this is to say, yes, the answer is both. The offense wouldn’t look nearly as bad if they had been making shots they normally make. However, their shot selection is not exactly laying the foundation for an elite offense each other. If the Celtics really are going to hit their ceiling they’ll need to make more shots, and probably create some better ones as well.

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