Nylon Calculus: What impact will Rudy Gay’s absence have on the Kings?

Rudy Gay tore his Achilles tendon on Wednesday and is out for the rest of the season, which begs the question: What impact will that have on a young Sacramento Kings team that has flirted with the eighth playoff spot in the Western Conference before recently sliding a few games out?

Gay was the second-leading scorer and rebounder on the Kings, one of only three players averaging double-figures and was their leading offensive threat from the wing. All told, this season Gay has averaged 18.7 points, 6.3 rebounds, 2.7 assists, 1.5 steals and 2.5 turnovers in 33.8 minutes per game, with a 55.9 true shooting percentage.

For fantasy sports, the question of interest would be to decide how Gay’s boxscore stats will be distributed among the other players on the team. However, in terms of actual impact on the Kings’ bottom line, that isn’t so important. What’s more important is to figure out what the team looks like, without Gay, at the bottom line.

A first pass way to do that might be to look at Gay’s plus-minus stats on the season. According to Basketball Reference, his on-court/off-court plus-minus is +11.7 — a raw value that states the Kings’ scoring margin per 100 possessions is 11.7 points better with Gay than without him. But before we put too much into that, we have to put it in context. In this case, a lot of context.

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A +11.7 on/off plus-minus would be VERY high for Gay, it would represent a significant career-high, in fact. In his last three seasons in Sacramento, Gay’s on/off plus-minus has been +2.4 (2014), +4.0 (2015), +2.0 (2016) and now +11.7 this season. Off the bat, that requires further examination.

Raw on/court off/court plus-minus is very noisy, especially before the season is over. Looking at a regressed plus-minus stat like ESPN’s RPM would be expected to give a more accurate result, and currently Gay’s RPM is +1.99, good for 49th in the NBA. This seems like a more reasonable estimate — a small net positive, but not monstrous impact. Gay is a high-volume wing scorer with average efficiency and a reasonably low assist percentage of 14.2. As a recent article corroborates, this type of player does generally have a small net positive impact that isn’t game-changing.

But returning to present data, why is Gay’s on/off plus-minus so much larger than expected? Is it an indication that the Kings’ bench is so weak on the wing that even Gay’s small positive impact was making a huge difference? Gay has already missed 11 games this season, while playing in 30, so let’s review the Kings’ performance in those games:

Gay plays (30 games): 11-19 record, Margin of Victory (MOV) of -0.8

Gay sits (11 games): 5-6 record, Margin of Victory -8.3

The MOV suggests the Kings really struggle in games Gay doesn’t play, but their win percentage is actually higher in games Gay sits. That’s a bit incongruous, though it could be a small sample size issue or even a real (if surprising) effect. Examine further.

In the first four games Gay sat this season, he was replaced in the starting lineup by either Omri Casspi or Garrett Temple. In one of those four games, DeMarcus Cousins also sat. Overall, in those four games, the Kings were outscored by 76 points for a MOV of -19.0. However, in the next seven games Gay sat, he was replaced in the starting lineup by Matt Barnes, and the Kings’ MOV was -2.1.

Suddenly, a clearer picture emerges. Gay’s plus-minus based impact estimates were greatly skewed by those first four games, but once the Kings settled on Barnes as a replacement their results have been more in-line with expectation for removing a small-positive impact player. Let’s look at a few recent season-long prior-informed-RAPM estimates for Gay and Barnes (2014 study by GotBuckets, 2015 & 2016 by Jeremias Englemann):

2014: Gay +0.3, Barnes +1.3

2015: Gay +0.7, Barnes +2.0

2016: Gay +0.0, Barnes -3.4

On the whole, both of these players are close to net-neutral impact players. Closer examination of those RAPM scores would indicate, as expected, Gay tended to score about a point higher on offense while Barnes was a bit less than that better on defense. But similar caliber. And thus far, through the small sample of seven games, replacing Gay with Barnes has led to a Kings team with a similar bottom line as it had with Gay.

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The Kings lost their second-leading scorer and rebounder, as well as their second-biggest name with Gay’s season-ending injury. They have replaced him with another veteran wing that tends to measure out with a similar estimated impact, and through seven games the team scoring margin was slightly higher but very similar with Barnes than with Gay.

The lineup change likely means that players like Darren Collison (currently third leading scorer on Kings) will be called upon to score more; the bench is weakened which could subsequently lead to more wear and injury; and there’s the possibility the perception of losing a key guy has a negative effect on a Kings locker room that already is volatile. But barring those types of not easily quantifiable changes, the early expectation is the Kings featuring Barnes on the wing should continue to perform at a similar, if slightly attenuated level to the way they performed with Gay on the wing.