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What Does ACR Tell Us About MLB Aces?
![By Keith Allison from Owings Mills, USA (Clayton Kershaw Uploaded by Muboshgu) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons](http://dev.rotoballer.com/wp-content/uploads/2014/05/Clayton-Kershaw-Los-Angeles-Dodgers.jpg)
In recent weeks I've been dabbling with a new statistic that I created to evaluate starting pitchers. This statistic is called Ace Composite Rating (ACR).
Up to this point, I've only used ACR to evaluate the starting pitchers for the Detroit Tigers. The calculations I arrived at using ACR numerically confirmed what I was seeing out of Tiger pitchers: that Max Scherzer and Anibal Sanchez had been their best pitchers, that Rick Porcello has pitched quite well, that Drew Smyly is fitting in nicely in the Detroit rotation, and that Justin Verlander is struggling mightily.
While the numbers I came up with using ACR passed the eye-test, they still lacked context. I needed to know the Ace Composite Rating for all starting pitchers in MLB before the statistic could really be useful to baseball fans or fantasy owners. Now that we've arrived at the All Star Break, it seems like a perfect time to find out how all those pitchers stack up thus far.
Using data from Baseball-Reference I pulled the numbers from the first half of the season on all starting pitchers with seven or more starts. The numbers included in the calculations for ACR are ERA, H/9, HR/9, BB/9, K/9, and IP/GS. I purposely avoided using any hard core sabermetric numbers in the calculations for ACR because I wanted the final number to be accessible for average baseball fans and useful for fantasy baseball owners. These are the top 25 starting pitchers in all of Major League Baseball through the first half of the season based on Ace Composite Rating.
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![By Keith Allison on Flickr (Original version) UCinternational (Crop) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons](http://dev.rotoballer.com/wp-content/uploads/2013/04/rotoballer-fantasy-baseball-advice-felix-hernandez-150x150.jpg)
If you're interested, you can see the how the rest of the starting pitchers in MLB stack up in terms of Ace Composite Rating right here. Be warned -- this chart is enormous. Still, for all you fantasy owners out there, it can definitely be useful if you're thinking of making some changes to your pitching staff over the All Star Break.
If you're not interested in wading through the entire chart, let me break it down for you. It turns out that the league average ACR for all starting pitchers with seven or more starts comes out to -3.16. That means that there have been 90 "above average" starting pitchers in all of MLB thus far. Once the ACR reaches the break-even point of 0, we're looking at about the best 33 starting pitchers in MLB, roughly the top 20%; meanwhile, the top 10% of starting pitchers all hold an ACR of 1.75 or better. And Clayton Kershaw is, well... on another planet.
With this information, I can tell you what I'm going to be doing during the All Star Break: I'm going to see where each of my starting pitchers stacks up in terms of ACR, and I'm going to see if there are any places I can upgrade via the waiver wire. I would recommend you do the same. There are more than a handful of pitchers who are above average in terms of ACR who are still available in many fantasy leagues. With a couple of well-informed moves, you could be blowing your competition away with pitching in no time.
Best of luck to all you RotoBallers in the second half of this MLB season.
