What's Khris Middleton worth in restricted free agency?

Bucks swingman Khris Middleton has suddenly transformed into an advanced stat NBA superstar; at least according to ESPN's all-in-one metric expressed in terms of points per 100 possessions, Real Plus-Minus (RPM). The operative word there may be "suddenly," as Middleton's ascension to sixth overall (!) on the RPM leaderboard happens to coincide with his chance at restricted free agency. The timing could have big implications for the Bucks, and it may have been a driving force in the deadline trade that freed up substantial salary cap space for Milwaukee and sent Brandon Knight to the Suns.

Or the operative word there may be "transformed." Middleton's 2014-15 RPM value (+2.03 ORPM, +4.10 DRPM, +6.13 overall) has him rubbing shoulders with NBA elites like LeBron James, Anthony Davis, Russell Westbrook, James Harden and Stephen Curry), but back in 2013-14 (+1.22 ORPM, -3.50 DRPM, -2.28 overall) he was slumming it up with guys like Omri Casspi, Austin Daye and Seth Curry. Here's a quick look at the year-to-year ratings and rankings:

Frank and I focused on the topic of Middleton's value in our latest trade reaction podcast episode:

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Some of the value in that table make sense to me. Middleton's skill for converting spot-up and cut/catch-and-shoot plays from the free-throw line extended, to the wings, and into the corners buoys his offensive value. His lack of dribble creativity and limited explosiveness cut down on free throw attempts and limit his offensive impact to (mostly) sharpshooting. Not that there's anything wrong with that.

A lost season with Larry Drew working in a confusing, chaotic system that forced him to bang with power forwards and bigger wings depressed his value on that end of the floor. Moving to the perimeter in Kidd's finely-tuned defense allows Khris to leverage his length, functional foot speed, active hands and defensive intelligence. His best defensive traits are optimized in this aggressive blitzing scheme. But even that explanation can't completely justify the quantum leap Middleton made in a single season.

To put this seismic shift into perspective, check out Nylon Calculus for Krishna Narsu's exploration of the largest improvements in RPM over the past year. Middleton's 8.21-point improvement from the past season to the current one is the single-highest jump in the entire league. The only other players to have a jump of 5.5 or more are, in order: Elliot Williams, Brandon Jennings, Donald Sloan, Dennis Schroder, Tyreke Evans, Cody Zeller, Meyers Leonard, and Amar'e Stoudemire. Let that list sink in for just a minute.

This isn't to say we should abandon metrics like RPM. These models seek to answer many of the important questions we ask when isolating player value (lineup context, team and opponent strength, value of individual contributions, etc.) and manage to apply the same rules and standards to every player in the association. That's the type of heavy lifting and dispassionate analysis our brains aren't well equipped to handle. So it's a nice starting point for conversations on player value.

The problem with a "black box" stat like RPM is that we don't have access to standard error and confidence interval information. We don't know how confident the model is in each projection. All of the ratings are presented in a simple, single-number format that (unfortunately) implies the same level of confidence for all ratings. We're left to our own devices to interpret when, where and why the model may be prone to huge swings.

So maybe it doesn't make sense to parse a statement about Khris Middleton's superstar status at all. The model doesn't do a great job accounting for role on a team, and it's unlikely that Middleton can become a primary option on offense because he can't do much to create his own shot. Likewise, you can't expect him to lock down the best scorer from opposing teams every night.

As restricted free agency approaches, here's my message: Let Khris be Khris. He's an excellent tertiary role player working in a defensive scheme that optimizes his value; a "3-and-D" expert playing in the perfect situation, doing his job as well as it can be done. Whatever you pay him as a restricted free agent, you should probably be prepared to keep Khris Middleton in his current role. That could make Chandler Parsons money ($15 million/year) tough to swallow, but the influx of cap space and cash from the massive new TV deal means it's time to redefine what "overpay" even means anymore. An Ersan-level deal of $8 million per year adjusts to roughly an $11 million per year contract when the cap jumps above $90 million, so keep that in mind.

At his current salary of $915,243, you can make the argument that Middleton is among the most valuable players in the NBA. But that salary is about to change. The key is to settle on a number that doesn't force him out of his optimized role. The Bucks have a great feel for how to maximize his skill set. There's real value in having that rapport and that knowledge heading into free agency. And with Brandon Knight gone from the offense the team gets a free look at what happens when you promote Middleton to a primary or secondary option.

Pay careful attention to the offensive experimentation down the stretch. It may just tell you how high the Bucks are willing go on Middleton when restricted free agency arrives.