Hitter xISO: June Update

I am humbled by the interest in my expected isolated power (xISO) equation since its inception. A fairly simple but helpful tool, I take solace in hoping it maybe has helped one fantasy owner identify a smart buy-low candidate — or reluctantly cut bait on Carlos Gonzalez. I also appreciate the feedback and recommendations for improvement and expansion. I will take care to consider their implementation when I have more available time.

It’s important to remember that Steamer and ZiPS also provide updated and rest-of-season (RoS) projections for most players. Hitter ISOs aren’t listed on the page listing all projections — only slugging (SLG) and batting average (BA) are included, forcing the user to perform some light arithmetic — but ISOs are listed on each hitter’s personal page. And they are not fundamentally different from the expected ISOs I have calculated for you today (spoiler alert). For reference, I crunched the correlation coefficients of every qualified hitter’s current xISO versus his current Steamer and ZiPS ISO projections:

Model: Update, RoS
Steamer: R = .828, R = .763
ZiPS: R = .835, R = .794

It makes sense that xISO correlates more strongly with the updated rather than rest-of-season projections as xISO is more descriptive than predictive. In other words, xISO explains what it thinks should have happened by now rather than what will continue to happen (although I take liberties to make such inferences when using the data by assuming a hitter’s batted ball profile remains constant). Steamer and ZiPS correlate much more strongly with each other — as they should, given they are highly sophisticated projection systems. Still, it’s a comfort and a validation to know that xISO, despite its lack of complexity, can hang with the big guns.

With some requests for more frequent xISO updates, I figured now would be a good time to check in on some of the noteworthy overperformers, underperformers and exactoperformers I highlighted three weeks ago.

It is comforting to see that several names mentioned in May regressed in the appropriate direction. Eric Hosmer, Joey Votto and Stephen Vogt saw their ISOs fall by 19, 26 and 27 points, respectively. Jake Marisnick hit the proverbial wall: over the course of three weeks, his ISO tanked by 57 points while his xISO held steady (.129 in mid-May, .123 on June 2).

However, on the other end of the spectrum, the underperformers fared — continue to fare — less remarkably. Troy Tulowitzki and Victor Martinez are still falling short of their xISOs in spectacular fashion, and the latter of them won’t have a chance to redeem himself anytime soon. Danny Santana has since closed the gap on his xISO, but it’s because of his falling xISO, not his rising ISO. Sometimes it’s the player’s batted ball profile that betrays us, not the outcomes of said batted balls.

Of the incredibly poorly named exactoperformers, only Mookie Betts has lost ground. (Alex Rodriguez has, too, but his ISO aligns with his xISO, which aligns with his declining batted ball profile. So, while his deceleration wasn’t necessarily foreseeable per xISO, it’s not currently unwarranted, either.) Betts’ appears to be the same hitter he has been all year, so if a fellow owner is demonstrating impatience with his current mini-slump, he may be worth your investment.

As with last time, please find below a table of the ISOs, xISOs and batted ball information of all 2015 qualified hitters (plus bonus Steamer and ZiPS numbers). Underachievers and their varying degrees of underachievement are highlighted in shades of red; overachievers, in blue.


Statistics exclude June 2 games.

xISO continues to validate the augmented power displays exhibited by Ryan Braun, Chris Davis, Lucas Duda, Prince Fielder, Ryan Howard, Charlie Blackmon, Brandon Belt and even Dexter Fowler (as well as the shrunken power of my man-crush Jose Abreu).

Once more, I’ll try to identify xISO underachievers who could bust slumps at any time. Here are five fresh names:

Matt Kemp, SDP OF

Name FB% Pull% Hard% ISO xISO diff Steamer RoS ZiPS RoS Steamer Update ZiPS Update
Matt Kemp 29.4% 38.8% 35.6% 0.082 0.183 -0.101 0.174 0.144 0.141 0.121

Well, that’s something. I ripped on the guy a bit two weeks ago, but I also noted he has nowhere to go but up. But I also said before that I wouldn’t blame you for dropping or selling him. He may have a power spurt up his sleeve. Or he may perform closer to his Steamer and ZiPS projections, in which I am more inclined to believe. But hey, here’s his name.

Yadier Molina, STL C

Name FB% Pull% Hard% ISO xISO diff Steamer RoS ZiPS RoS Steamer Update ZiPS Update
Yadier Molina 32.9% 41.8% 26.1% 0.052 0.147 -0.095 0.120 0.116 0.094 0.094

If you’re hurting at catcher, Molina’s zero bombs might already be the reason why. He simply can’t go on hitting zero home runs forever, however. xISO expects 2013 numbers, whereas Steamer and ZiPS expect the lesser 2014 version of Yadi. Regardless, he’s due, as they say, so be patient.

Evan Longoria, TBR 3B

Name FB% Pull% Hard% ISO xISO diff Steamer RoS ZiPS RoS Steamer Update ZiPS Update
Evan Longoria 42.6% 43.2% 35.8% 0.148 0.223 -0.075 0.185 0.178 0.173 0.168

It’s becoming clear that Steamer and ZiPS are less bullish on the largest outliers. xISO expects a full rebound to 2013 levels for Longoria, whereas Steamer and ZiPS expect something in between 2013 and 2014 levels. Still, his home run pace ought to pick up a bit.

Robinson Cano, SEA 2B

Name FB% Pull% Hard% ISO xISO diff Steamer RoS ZiPS RoS Steamer Update ZiPS Update
Robinson Cano 24.7% 38.6% 34.3% 0.090 0.165 -0.075 0.155 0.142 0.133 0.125

This contract looked bad when it happened. It looked even worse when 2014 happened. It looks profoundly worse now, knowing that Cano, despite seemingly suffering some bad luck right now, may never regain his form. If I had to bet on anyone to scrounge together 60 points of batting average and isolated power apiece, it would be Cano, but he’s simply not the potential first-rounder he used to be — or, really, anything close to it.

Jorge Soler, CHC OF

Name FB% Pull% Hard% ISO xISO diff Steamer RoS ZiPS RoS Steamer Update ZiPS Update
Jorge Soler 28.2% 36.3% 39.5% 0.138 0.195 -0.057 0.180 0.186 0.165 0.165

Here’s one thing on which the projections and I can agree: Soler hits the snot out of the ball. And although he’s not demonstrating anything that remotely resembles the plate discipline that made him a lock for stardom, he does seem to be getting unlucky on his hard-hit balls in play. I’m sure his lack of production is killing you the same way it’s killing me, but hang tight. (News of a potential DL stint isn’t too enticing, though.)

We hoped you liked reading Hitter xISO: June Update by Alex Chamberlain!

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Currently investigating the relationship between pitcher effectiveness and beard density. Biased toward a nicely rolled baseball pant. Reigning FSWA Baseball Writer of the Year and 5-time award finalist. Featured in Lindy's Sports' Fantasy Baseball magazine (2018, 2019). Now a Tout Wars competitor.

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Mike W.
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Mike W.

The big concern I have with Soler is that right now he is actually getting somewhat lucky with his BABiP. When/if that falls off, his production could be even worse than it is right now.

I don’t think I would drop him, but I am selling him if I can still get a decent return. Maybe I’m just down on him since he was a top 80 pick in a lot of drafts.