Expected Effective Field Goal Percentage: 2019-20 Midseason Recap

Lynne Sladky – Associated Press

Last season, I introduced Expected Effective Field Goal Percentage (XeFG%). In short, the statistic predicts the effective field goal percentage (eFG%) a league-average player would have if they attempted the same shots as any given player. A player with a high XeFG% takes high percentage shots, while a player with a low XeFG% takes low percentage shots. The purpose is to add context to traditional shooting metrics like effective field goal percentage. Instead of simply taking a player’s eFG% at face value, you can compare it to their XeFG% to see whether they are performing above or below expectation. For more specific details about XeFG%, including how it’s calculated and its flaws, you can read the initial article explaining it here.

The NBA All-Star break just ended, so I thought I’d give a quick midseason update to two of The Spax’s advanced basketball metrics: XeFG% and DXeFG%. In this article, I’m using the code detailed here for all of the calculations. The full XeFG% and DXeFG% data can be found through the site’s navigation bar.

Offensive Efficiency

The size of each dot represents the total number of field goal attempts for each player.

The straight line through the graph is the expectation curve (y=x line). A dot above the expectation curve represents a player performing above expectation, while the area below the curve consists of the underperformers. I only labeled a few noteworthy points on the graph and my commentary will only scratch the surface of what the data has to offer, so feel free to see the full numbers for yourself here.

One of the first things I noticed was Duncan Robinson’s location at the top center of the chart. The 25-year-old Miami Heat guard/forward has broke out as one of the league’s most lethal outside shooters. He has hit 192 3-pointers through 55 games this season at a blistering clip of 43.2%. Only three players have hit more threes than Robinson this season, and Lillard’s 3P% of 39.3% is the highest among them. He’s been a huge part of the Heat’s surprising rise this season. They’re currently holding the four seed in the Eastern Conference with a 35-20 win-loss record, and young players like Bam Adebayo, Kendrick Nunn, Tyler Herro, and Duncan Robinson have played a large role in their success.

Of the top-60 players in the NBA in three-point attempts this season, only one player has a higher 3P% than Duncan Robinson: JJ Redick. The 35-year-old shooting guard for the New Orleans Pelicans is enjoying the most efficient season of his career. He’s connecting on 45.8% of his 3-point attempts and his eFG% of 59.6% is a career high. Redick’s veteran presence is invaluable on a team with as many youngsters as the Pelicans. Brandon Ingram, Lonzo Ball, Frank Jackson, Jaxson Hayes, Nickeil Alexander-Walker, and Zion Williamson all get playtime for the Pelicans. Lonzo Ball is the oldest of those players at 22-year-old.

While Robinson and Redick have enjoyed great seasons, Khris Middleton has them beat. Middleton is having the best season of his career by far. He’s putting up 20.6 PPG with an 58.7% eFG%. Before this season, his single-season career high eFG% was 53.0% in 2015. The 28-year-old forward is playing the best basketball of his career and it’s contributing to the Milwaukee Bucks’ status as the league’s best team. They have 47 wins through 55 games and they’ve shown no signs of slowing down.

On the other side of the expectation curve, you might notice something that we’ve seen in past years as well: inefficient rookies.

Jordan Poole’s inefficiency has gotten to the point where it’s almost impressive. He’s hitting just 26.6% of his three-point attempts. Things aren’t much better inside the arc, either, where his field goal percentage is a meager 34.2%. All things considered, Poole’s eFG% of 37.3% is the lowest in the NBA. Behind Poole with the second and third-lowest eFG% in the NBA this season are fellow rookies Cam Reddish and RJ Barrett. Of course, they’re still extremely young. None of them are even old enough to legally drink alcohol yet. They have plenty of time to improve their game.

Defensive Efficiency

The size of each dot represents the total number of field goal attempts defended for each player.

On this graph, a dot below the expectation curve is good because it means opposing players are less efficient than expected when guarded by that player.

So, it’s no surprise that the three best (arguably) defensive players in the league this season are all lumped together at the bottom center of this graph. Rudy Gobert, Giannis Antetokounmpo, and Anthony Davis are the three clear front runners in the NBA Defensive Player of the Year race. Davis is currently the favorite, as he’s leading the Los Angeles Lakers to a 106.52 adjusted defensive rating, the second-best in the league. Meanwhile, Rudy Gobert is still arguably the most valuable defensive player in basketball. However, the Jazz are not as successful as the Lakers or Clippers, and he might suffer from voter fatigue as well after winning the last two DPOY awards. Giannis will likely take a hit in the voting as well due to the fact that he’s just not as valuable as his competitors — just look at his teammate Brook Lopez. It’s looking like Anthony Davis will end up taking home the award, but there’s plenty of basketball left to be played.

At the top of the graph, we can see the least efficient defenders in the league this year. Among them are actually three starters for the Cleveland Cavaliers. Yeah, it’s quite remarkable that the three players allowing the highest eFG% all start for the same team. It’s not exactly surprising to see Sexton and Garland. The two young guards are not exactly known for their defense, and Sexton posted some of the worst defensive numbers last year as well. However, it’s by far the worst defensive season of Kevin Love’s career. Maybe it’s exacerbated by him having to share the court with Sexton and Garland. Maybe it’s the result of him playing for an awful team and not caring about putting in effort now that he’s secured the bag. Maybe he’s just gotten worse at basketball. Or maybe it’s a little bit of everything.

There’s plenty of more things that I could analyze, but I’ll leave it at that. Once again, you can see the XeFG% data here and the DXeFG% data here. As always, the full player data will be in the XeFG% and DXeFG% tabs under ‘NBA’ on the site menu.

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