2017-18 Answers: Plus-Minus Machines

Four players who excelled in plus-minus stats switched teams before last season. What did we learn from their performance?

I debuted Cleaning the Glass Insider last year with three articles that detailed the big-picture questions I had about the coming season. As I wrote:

There’s a lot to be excited about when the NBA starts again, but for me no part of it is more exciting than that feeling of suspense as we get ready to find out how all of the new teams, new players, and new schemes play out. We get to learn the answers to our questions.

Today, the third and final question I asked: Will the plus-minus machines keep humming on new teams?

When I asked this question before last season, I started off by introducing the pros and cons of relying on plus-minus in its various forms for player evaluation, concluding by writing:

>One helpful rule of thumb: the more data, across more teams and in more roles, the more confidence we have that these metrics are picking up on something real and repeatable…But a front office, of course, can’t wait until a player’s career is done to judge whether these metrics were picking up on something real.

That led right into what I wanted to watch in the 2017-18 season:

>Four players changed teams this summer that have looked much better by plus-minus metrics than their conventional reputations would suggest: Ricky Rubio, Jae Crowder, Amir Johnson, and Patrick Patterson. For each of them there are reasons to think the plus-minus is picking up on something real, and for each there are reasons to be skeptical.

That all four players changed teams in the same offseason provided a nice test. Decision-makers who might be swayed to acquire a player because of his strongly positive plus-minus (or high rating in one of its adjusted flavors, like ESPN’s Real Plus-Minus) could watch these cases and see how much they could count on that performance continuing. All of them had a good-sized track record, across multiple teams and roles, to suggest that their plus-minus was picking up on something real. Now we could see how robust it was.

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