What’s wrong with the Boston Celtics’ outside shooting?

It wasn’t supposed to be like this. The Celtics weren’t supposed to be 27th in offensive rating. They weren’t supposed to be shooting just 35% from deep. And they definitely weren’t supposed to be struggling to beat teams like the New York Knicks or the Orlando Magic (as of the writing of this blog, those two teams are a combined 8–15, playing to the tune of a 0.348 win percentage).

No, these Celtics were supposed to be the main challenger to the behemoth that is the Golden State Warriors. With five unselfish starters who had all shot at or above 40% from deep in their last healthy season, coupled with a deep bench dubbed the “BWA”, and the brightest young head coach in the NBA, these Celtics were destined to take the throne of the East after LeBron James left for Los Angeles and his business interests.

That hasn’t happened yet, and although the season is still young and players are adjusting to their roles, there are still some concerns and issues that need to be ironed out if the Celtics have any hope of raising Banner 18 in the next year. Here’s a look at one trend in particular that may be the culprit behind their slow start — their poor three point shooting.

Say it with me: Kyrie Irving, Jaylen Brown, Jayson Tatum, Gordon Hayward, and Al Horford. The starting lineup. The Five Leaf Clover. The Newport 5. Whatever you want to call them. That lineup might be the most talented five man unit in any city not named Oakland. Take a look at their percentages from deep in their last healthy season in the figure below. Everyone is in the 40% range — typically considered elite territory. These guys should all be able to space the floor for each other, hit 3’s at an high level, and open up the floor for driving lanes for others.

Last year’s 3 point shooting percentage for every member of the Celtics’ starting lineup (Hayward’s percentage is from his last healthy season with Utah in 2016–17)

Except, that hasn’t really been the case. The numbers this year are almost shocking:

2018–19 3 point shooting percentage for every member of the Celtics’ starting lineup. In short: it’s ugly.

With the exception of Irving, everyone else on the list has seen their percentages fall down drastically. It was natural to expect a slow start form Hayward, as he reacclimates himself to the NBA game after a year of recovery. Shooting from a chair or in an empty gym is different from shooting in an NBA game with a defender chasing you down and the fatigue setting in. He needs time to get his legs under him, and the poor shooting is not a shock. However, for Brown, Tatum, and Horford? The decrease in efficiency is stunning.

Is this a case of regression to the mean? Maybe, maybe not. Let’s go through each player:

  • Brown did struggle with his shooting in college, was a mediocre shooter in his rookie season, and still hasn’t figured out his free-throw shooting woes (career 65.5% from the free-throw line). There are some in the basketball world who believe that free-throw shooting is a better indicator of a player’s shooting talent than 3 point percentage. If we want to believe this, then maybe Brown is just showing his true colors and regressing into an mediocre/inefficient 3 point shooter. But I don’t buy that. He did shoot 39% in the playoffs as the team’s #1 option, taking over 6 threes a game against playoff-caliber defense. I would think that if a player was a poor shooter, the playoff intensity would be where we’d see the regression, not 10 regular season games.
  • The free throw shooting proposal wouldn’t apply to Tatum, however, who has had no such struggles at the free-throw line in his college or NBA career. Tatum is shooting nearly 90% from the line this year; that’s not the mark of a poor shooter. His playoff three point percentage of 32.4% may be something to keep an eye on, but he was also just 20 years old, thrown into the spotlight and asked to lead the team in scoring.
  • For Horford, a similar reasoning is applicable. A career 75% free-throw shooter, Horford has expanded his range over the last three seasons, attempting over 3 threes a game and knocking them down at increasing efficiency each season. Maybe Father Time is finally catching up to Horford a little early? He turned 32 over the summer, and while his style of play should allow him to age gracefully in his final 4–5 NBA seasons, a regression to this magnitude is also unlikely.

No, this doesn’t seem to be a case of regression to the mean. Why then is this team shooting just 35% from beyond the arc? There has to be another reason.

A look at the types of shots may give us a better glimpse at that. Are teams simply defending the Celtics better? Are the Celtics not generating good looks? Are they missing open shots? Are their open shots going to poor shooters? Let’s take a look at the quality of shots Brad Stevens’ system is generating.

The cool thing about the NBA Stats database is that it allows you to see the types of shots teams are generating. Specifically, I want to look at “Wide Open” three point attempts. NBA.com defines a shot to be “wide open” if the closest defender is 6+ feet away. See the points below for what I hope is a concise summary of the data:

  • The Celtics generate 19.7 “wide open” 3 point attempts per game. This is 3rd best in the NBA, and these 19.7 “wide open” attempts represent over 22% of the Celtics’ total shot attempts.
  • The Celtics shoot 35.6% on these “wide open” 3 point attempts. This is tied to 6th worst in the NBA.

What can we conclude from this data? Well, first of all, the Celtics offense is working in the sense that it is generating open shot attempts. But it’s important to generate these open shot attempts for good shooters, not the poor shooters that the defense wants to leave unguarded. So, who are the beneficiaries of these open looks?

  • Al Horford, who takes 4.3 “wide open” threes a game, and is shooting a paltry 27.9% on those looks. Horford shot 43.6% on these same “wide open” looks last year.
  • Jaylen Brown, who takes 2.0 “wide open” threes a game, and is shooting 33.3% on those looks. Brown shot 43.8% on these same “wide open” looks last year.
  • Jayson Tatum, who takes 1.7 “wide open” threes a game, and is shooting just 23.5% on those looks. Tatum shot 46.6% on these same “wide open” looks last year.
  • Kyrie Irving, who takes 1.3 “wide open” threes a game, and is shooting 30.8% on those looks. Irving shot 38.7% on these same “wide open” looks last year.

So, what does this tell us? The Celtics seem to be getting the shots they want for the shooters they want taking those shots. Brad Stevens is doing his job. His offense is getting the looks that this team needs. Unfortunately, the shots just haven’t been falling. I would expect that to change soon. All it takes is one hot stretch of games, and suddenly the Celtics could be back in the upper half of the league in offensive rating.

Disclaimer: the NBA.com shot dashboard data is sometimes a little wonky and may not be 100% accurate

So where do we go from here? Well, first, I would expect the shooting to reverse course shortly. This team just has too many talented guys to be shooting this poorly. Surely, there are other issues, like too much isolation and long midrange shots, and not enough drives to the rim. But the root of those problems may be in the three point shooting. Make more of your open looks, and opponents have to stay on you, which spaces the floor and allows guys like Kyrie or Brown to attack the rim, generate points in the paint, and get to the free throw line.

Additionally, the schedule the Celtics have played has been tough. Some metrics have said it has been anywhere from the hardest to the 8th hardest schedule of any team so far. And it doesn’t really ease up until November 17th when they play the Utah Jazz. But after that game, they have a solid 30 days worth of games against beatable opponents. From November 19th to December 19th, they play at least one game against each of the Hornets, Knicks, Hawks, Mavs, Pelicans, Cavs, Timberwolves, Bulls, Wizards, Pistons, and Suns. If they don’t take their opponents lightly, that month could give us a few long winning streaks. Keep that in mind as you watch Toronto rising up the standings at the moment.

My inspiration for this post was a tweet by Alex Kungu, who writes for CelticsBlog. I wanted to build off of his observation and try to give more stats player by player. Go follow Alex on twitter @Kungu_NBA if you’re not already. He writes the good stuff.