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Is Trevor Cahill a Big Loss? Part Two

December 11, 2011


Yesterday I looked into whether or not Trevor Cahill‘s departure represents a big loss for the Oakland A’s and concluded that with where the A’s are headed (non-contention while building to contend in 2015 or so) and with Cahill’s poor past performance that ultimately it isn’t a big loss. A few points were brought up though, Nathaniel Stoltz of the great Seedlings to Stars asked me whether or not the numbers I quoted in my chart where Cahill was over or under the league average whether they were for starting pitchers exclusively or pitchers as a whole. They were for pitchers as a whole, however regardless the numbers still find Cahill below average for starting pitchers as well on the K/9. He also highlighted that I omitted one of Cahill’s most defining qualities, his high groundball rate. That is correct and it was an omission. Cahill has far surpassed the GB% every year he has been in the majors:

Cahill GB% MLB GB%
2009 47.8% 43.3%
2010 56.0% 44.4%
2011 55.9% 44.4%

What does this really mean? Ground ball pitchers have their advantages – they give up fewer home runs than non-ground ball pitchers, obviously ground balls seldom leave the yard – yet even here Cahill doesn’t differentiate himself. Let’s look at pitchers who have similar GB% to Cahill over the span of 2009-2011.

 2009-2011 GB% HR/9 HR/FB
Ricky Romero 54.6% 0.87


Jaime Garcia 54.6% 0.60


Brett Anderson 53.5% 0.82


Trevor Cahill 53.3% 1.00


Charlie Morton 53.1% 0.72


John Lannan 52.5% 0.86


Felix Hernandez 52.5% 0.64


Jhoulys Chacin

52.4% 0.81


It is noteworthy that Cahill, despite playing in one of MLB’s most home run unfriendly parks has the highest HR/9 rating of all these pitchers, owing to his higher than all the other pitchers’ 12.1% HR/FB. But one might say, hey I am including the outlier year of 2009 when Cahill a rookie had a far different GB% than the other two years, fair enough:

2010-2011 GB% HR/9 HR/FB
Derek Lowe 58.9% 0.76


Jake Westbrook 57.8% 0.84


Justin Masterson 57.3% 0.57


Trevor Cahill 56.0% 0.85


Fausto Carmona 55.2% 0.88


Ricky Romero 54.9% 0.85


Jaime Garcia 54.6% 0.60


Cahill ends up a little worse than average – the very essence of what I am arguing Cahill is – now despite posting one of the highest (fifth) groundball rates during this period. And again we must remember that this is being done at the Coliseum, whereas guys others on this list pitch in far worse environments for surrendering home runs. As stated in this great article by David Gassko in the Hardball Times

“There are certain advantages to having a high ground ball rate—like a low home run rate—and certain disadvantages, like a high line drive rate and more unearned runs. The fact is, just like any other pitcher, ground ball pitchers can be successful and unsuccessful, based on how well they do other things, like controlling the strike zone. But the ability to prevent balls from being hit in the air itself is not all that important; certainly not as much as some would like you to believe. “

Cahill doesn’t take advantage of the one great advantage of being a ground ball pitcher. To his benefit he doesn’t allow a higher amount of line drives though, a key disadvantage as line drives are most likely of any type of contact to result in a hit. See how Cahill betters these figures:

2009 18.1% 18.9% .272 .295
2010 15.0% 18.2% .236 .293
2011 18.8% 19.6% .302 .291

He is consistently below league average on line drive % and you can see that when his line drive percentage is higher, the BABIP is higher too which isn’t altogether surprising. So this is somewhere where Cahill is good, why am I saying this is a negative? Because he doesn’t keep balls in the park like he should on HR/9 and despite allowing fewer line drives than we expect it doesn’t offset the negative very much, the very definition of average and/or mediocre.

No matter how you slice it, Cahill is not an elite pitcher, his upside is likely not much greater than what we have seen thus far. He may be a smart guy, he may be adaptable, but thus far he has been consistently inconsistent and until that changes, calling him a front-of-the-rotation guy is severely misguided.


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