Park-Adjusted Z-Scores thru 7/11

Coming up on the All Star Break is always a nice opportunity to look back and reflect on long term trends throughout the season. Even if it isn’t a speed sign mile marker (percent ending in 5 or 0) it’s a stopping point that has been ingrained in fans since time immemorial. I’m going to park-adjust a couple of key statistics using this method and the 2013 Fangraphs Park Factors.

You can download the excel file by following the link, clicking on file, and then clicking on download from within that dropdown. I’d recommend it if you want to follow along throughout this. The initial data download from Fangraphs can be found on the “Raw” tab, while the park-adjusted figures are on the “Adjusted” tab.

Z-scores are a handy tool because they take into account how many standard deviations the player is from the mean within a population. The player pool here is all non-pitcher batters with >0 PA. This pool yields the following summary statistics for each of our relevant categories:

Statistic/Mean Standard/Deviation

Plate Appearance/183/128

Batting Average/.255/.071

On-Base Percentage/.318/.078

Slugging Percentage/.397/.125

Isolated Slugging Percentage/.142/.075

Strikeout Percentage/19.8%/11.0%

Walk Percentage/8.0%/4.3%

If a player was exactly at the average of each of these then that player would have a Z-score of 0. I have filtered out the players with less than 50 PA on the Adjusted sheet in order to remove some of the smallest samples. Know that these players are still included in the summary statistics that back the Z-scores. Let’s walk through a player from the sheet to give examples.

Mike Trout’s 389 PA lead to a Z-score of 1.6, while his BA, OBP, and SLG are 0.8, 1.1, and 1.7 deviations better than the average, respectively. Moving on to his components of ISO, K%, and BB% we see scores of 2.1, -0.3, and 1.3, respectively. Note that I have inverted K% so that the higher the Z-Score, the lower the K%. We can then total all of this up to get a total score of 8.3 which leads all batters. Mike Trout is pretty good. I have done this for all batters throughout the player pool so go through and look at your favorites. Here’s the top-25:


(Click to enlarge blahblahblah)

Most of the names are familiar, though Seth Smith, Derek Norris, SVS, and J.D. Martinez are some guys that you probably wouldn’t have put on this list to start the year. How about the other side of this coin? The dirty side:



Ugh, so dusty. The biggest surprise, to me, is that Jose Molina isn’t the worst!! He’s still pretty bad and he’s joined by a bunch of other guys that are good at thing other than swinging a bat or are on the verge of getting a pink tag. Since this is a Rays site, where do our batters rank:



At 45th amongst players with more than 50 PA Ben Zobrist leads the team here by not really having a weakness. He’s average or better across the board and plays a lot. Even with his DL stint earlier this year. David DeJesus has a similar case. Kevin Kiermaier comes in next, though his walk rate and late start to the year take away from his incredible power, thus far. Then we get to the face of the franchise who’s ISO is surprisingly below average. The underrated Desmond Jennings comes in next. His walk rate has been his best skill so far, which is good, considering he’s the fastest player on the team. And so on. Note that the Rays have 10 above-average players, with no everyday regular being in the negative.




About Jason Hanselman

Rays fan.
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