The Cleveland Cavaliers have plenty of problems right now, and many of them concern their struggles on defense. Through two games in these Eastern Conference finals — both losses — they’re allowing 112.8 points per 100 possessions against a Boston Celtics team that averaged only 105.2 during the regular season (according to Advanced NBA Stats). They’ve been torched by Jaylen Brown (who’s scored 23 each game) and they have no answer for the threat Al Horford poses from both the inside and outside.

But the Cavs being inept on defense is not really breaking news. They’ve ranked among the league’s worst at that end of the floor all season. Instead, they win games with their offense, and not just because LeBron James can decide to take over games whenever he wants (although that helps). More than perhaps any other team in the NBA, the Cavs’ fortunes rise and fall based on how well they knock down shots from the perimeter. And they’d better heat up soon against the Celtics, or their bid for a fourth consecutive East title will clang harmlessly off the rim like so many of their 3-point shots.

The playoffs have helped crystallize the Cavaliers’ reputation as a team that lives and dies by its shooting. This is, after all, the same group who struggled to get past the Indiana Pacers while making only 32 percent of their 3-pointers, then turned around and hit 41 percent from deep while steamrolling the Raptors a week later. Even during the regular season, though, Cleveland was unusually dependent on the hotness of its shooting hand: In wins, the Cavs made threes at a 41 percent clip, versus just 31 percent in losses — a 10-percentage-point gap that was the biggest in the league. And that regular-season gap has only widened, to nearly 11 percentage points, during the playoffs.

Every team shoots better in wins than losses; making shots is kind of the point of the game, after all. But some teams can get by during poor shooting nights more readily than others. The Minnesota Timberwolves, for instance, were as good on offense as the Cavs this season, but they had the league’s third-smallest difference between their 3-point percentage in wins and losses (3 percentage points) because they didn’t really rely on threes for a strong offensive performance. For the Cavs, though, threes are the leading indicator of their overall health as a team. Here are the correlations between various metrics and Cleveland’s efficiency margin in each game this season:

Three-point accuracy determines Cleveland’s fate Correlation between the Cavaliers’ efficiency differentials and various metrics for games in the 2017-18 season, through May 16 Metric Correlation with the Cavaliers’ efficiency Cavaliers’ 3-point % +0.58 Cavaliers’ steal % +0.36 Opponents’ turnover % +0.36 Cavaliers’ free throw % +0.32 Cavaliers’ 2-point % +0.32 Opponents’ 3-point % -0.30 Opponents’ offensive rebound % -0.26 Opponents’ steal % -0.23 Opponents’ 2-point % -0.22 Cavaliers’ turnover % -0.19 Cavaliers’ assist % +0.13 Cavaliers’ offensive rebound % +0.13 Opponents’ assist % -0.12 Opponents’ block % -0.09 Cavaliers’ FTA/FGA +0.05 Pace -0.04 Opponents’ FTA/FGA -0.02 Opponents’ 3PA/FGA +0.01 Opponents’ free throw % -0.01 Cavaliers’ block % +0.00 Cavaliers’ 3PA/FGA +0.00 Source: Basketball-Reference.com

By far the statistic that tracked most closely with the Cavaliers’ overall efficiency in any given game was their 3-point percentage, which had a correlation coefficient of 0.58. (By comparison, the correlation between the Warriors’ 3-point percentage and their efficiency margin was 0.44; for the Rockets, the correlation was 0.38; and for the Celtics, it was 0.28.)

Now, it is fair to ask which direction the causation goes here. The Cavs’ offense is mainly predicated on LeBron James coming off a ball screen and either creating for himself or finding the open man when the opponent brings help. And certainly James himself has taken on a huge percentage of Cleveland’s 3-point shooting load. So maybe the Cavs are simply getting better looks because the rest of their offense — i.e., LeBron — is functioning at a higher level. (For example, the Cavs have shot a very healthy 20-for-32 on passes from James in the Eastern Conference Finals so far.)

But if LeBron is generating more open shots only in games where the Cavs are rolling, it’s not showing up in the numbers. According to Second Spectrum’s Quantified Shot Quality metric (which calculates an expected shooting percentage for each shot based on its difficulty), Cleveland doesn’t tend to get better deep looks in its good games than its bad ones. In wins during the playoffs, the Cavs have an expected effective field goal percentage of 52.4 percent on 3-pointers; in losses, that number barely drops, to 52.0 percent. Instead, it’s Cleveland’s ability to capitalize on those 3-pointers that has varied wildly: from an eFG% 4.4 points higher than expected in postseason wins to one 10.6 points lower than expected in losses.

Game 2 against Boston was a great case study of Cleveland’s Jekyll-and-Hyde shooting tendencies. In the first half, the Cavs built a 7-point lead while going 7-for-14 (50 percent) from deep; in the second half, they watched that lead slip away as they shot a dismal 3-for-17 (18 percent) from beyond the arc. Their shot quality on threes (again according to Second Spectrum) declined by 2.1 points of expected eFG% between halves, so the Celtics did a better job of challenging the Cavs’ shooters as the game went on. But a far bigger factor in Cleveland’s decline was its massive 35-point drop in eFG% versus expected — in other words, the kind of streaky variance that can’t be explained by shot quality alone.

And what does explain it? Maybe the Cavs shoot so many threes — they’re third in the playoffs in attempts per game — that they’re bound to run up stretches of good- and bad-shooting games like this. Or maybe they’re just collectively trying to provide further evidence that the hot hand really does exist. Whatever the explanation, Cleveland has to hope that its shooting starts fluctuating in the opposite direction, and fast. Because not even James, with his 42 points, 12 assists and 10 rebounds in Game 2, could keep the Cavs from digging themselves a deeper hole in this series.

We’ve seen the Cavaliers brush off these kinds of cold shooting performances in the past, burying opponents under an onslaught of threes that can make you wonder how they ever got cold in the first place. But that’s also the point: Cleveland needs a sustained 3-point resurgence if it’s going to claw its way back against the Celtics. As crucial as LeBron’s production is to the Cavs, it might be just as important for his teammates to step up and knock down their shots when they get the chance.

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