Will Arizona’s Home Run Woes Continue?

In case you missed it, Ryan and I have begun contributing over at Beyond the Box Score as of three weeks ago. During our short stint there to date, we’ve published some really good stuff and I encourage you to head over there and check out our work and the writing of our saber-savvy colleagues. I’m bringing this up because I recently published a piece in which I studied home run rates and which types of starting pitchers tend to give up the most home runs. This is applicable because, as you’ve probably noticed, the Diamondbacks gave up a lot of home runs last year and I now want to apply the more general findings of my study specifically to the Diamondbacks’ rotation.

While I’d suggest that you read the whole article, I’ll quickly summarize my findings below. When compared to pitchers who give up very few home runs, the starting pitchers that give up home runs with the greatest frequency tend to:

• rely heavily on four-seam fastballs
• have low average fastball velocities
• don’t have the raw stuff to generate swings and misses out of the zone

Now, let’s have a look at how the Diamondbacks’ rotation lines up with these findings.

*Z-Swing% = percentage of pitches in the zone that were swung at

*O-Swing% = percentage of pitches outside of the zone that were swung at

To be honest, the Diamondbacks rotation was decent at limiting home runs last season. The median home run rate (HR/9) among qualified starters in 2013 was 0.88 and Arizona has two guys under that threshold, one guy right at that rate, one guy just over it and one guy way, way above. Of course, the median rate is just “average” and if there’s anything the Diamondbacks don’t want to be going forward, it’s average. Instead of looking at the whole team, let’s take it case-by-case.

Patrick Corbin

On top of being the rotation’s anchor, Corbin was also the stingiest with the long ball. As my earlier findings suggested, a reliance on a fastball other than a four-seamer was beneficial and Corbin throws a two-seam fastball the majority of the time. With an average velocity of 92.1 mph, he has adequate, if not overwhelming, velocity. In addition to this, his ability to get hitters to chase out of the zone is tops on the staff. This, of course, is due to his absolutely nasty slider, which either generates strikeouts or weak contact. Corbin’s home run rate should maintain a level below average with this recipe, especially if he can add a changeup to help against righties.

Wade Miley

Miley logged over 200 innings last year but was bitten by the long ball. He does throw a two-seamer primarily, but the velocity leaves something to be desired. Of more concern is his inability to get hitters to expand the zone and this underlies his problem with a dominant secondary offering. His changeup profiles as his best pitch but it’s not necessarily a great swing-and-miss offering. Outside of that, his curve is functional but hardly anything to get excited about. He’ll likely always struggle at having anything lower than an average home run rate.

Trevor Cahill

At 0.82, Cahill was safely below the average home run rate. His sinker generates a ton of ground balls, which could be whiffs if his velocity were better. With that said, he generates even fewer swings at pitches outside of the zone than Miley, also showing that he lacks a strong swing-and-miss secondary pitch. Like Wade, his changeup is his best secondary offering but it’s less effective that Miley’s. These two actually profile as very similar pitchers, aside from their handedness. Because of the sinker, he’ll likely keep the ball in the yard at a similar rate to which he did in 2013.

Brandon McCarthy

McCarthy was right at the median home run rate, which was a little surprising considering he has the 18th-lowest home run rate among qualified starters with over 250IP over the last three years. It was actually his highest home run rate in the last three seasons, which might be concerning. By throwing a heavy dose of two-seam and cut-fastballs, he shouldn’t give up a lot of hard contact. Of course, we know how that worked out last year. I’m buying McCarthy as a bounce-back candidate as his BABIP was unsustainably high and he should yield fewer home runs going forward based on my study.

Randall Delgado

Well, here’s your outlier. Delgado gave up a ton of home runs last season; in fact, the second most of any pitcher with over 100 innings-pitched (thank you, Joe Blanton). Delgado used almost an equal distribution of four and two-seam fastballs, both averaging just over 90 mph. That’s not good velocity. Ok, so he doesn’t throw hard, but that’s not necessarily the problem. There are plenty of guys who throw 89-92 with success, at least the success required to be a number five starter. Oddly enough, he was actually slightly better with the straight fast ball (four-seam) than the one with sink and fade (two-seam), which is abnormal given my study. Where he really got hurt was with the curveball because when he didn’t bury it, he hung it.

Batters chased Delgado’s pitches out of the zone more than either Miley or Cahill, which shows that he has some ability to deceive hitters, at least compared to those two. His changeup is his best pitch and it is capable of generating whiffs. He’s going to have to do a better job, however, of using his fastball to get ahead so he can utilize the change or keep his fastballs down, where they belongs given their lack of velocity, to induce more grounders. I’m in favor of eschewing some of the four-seamers and believe that with some growth of the two-seam fastball and maybe a little improvement with the curve, Delgado can be quite useful at the end of the rotation. These improvements will help him limit fly balls and, subsequently, home runs.

There’s no way his HR/9 stays so astronomically high. Even though he had his struggles, they don’t support a home run rate of that magnitude and he was simply unlucky some of the time. Some of the poor luck was his fault (falling behind with the fastball, hung curves), but some of it was not and we should expect better numbers from him going into 2014. Players of his age are far from complete and he’s either going to continue to grow (most likely) or he’s going to flame out.

When it’s all said and done, the Diamondbacks gave up home runs at a roughly average rate last year. Delgado skewed that average with his multitudes of dingers allowed, but the others were well within the range of normal or better. Corbin should keep limiting the homers, Miley will always give up his, and McCarthy and Cahill should be expected to be around league average if not slightly below. Delgado’s the wild card and while I see significant improvement from him next season in the home run department, his lack of velocity and a good secondary offering to pair with his changeup is worrisome to a degree. I’d personally like to see him master and use the two-seamer more to induce more grounders, but he’s going to have to hone it first.

This is something I’ll be watching for in Spring Training and I’ll try to let you know what I observe.

(*Note: I’m aware that a lot of the home runs were given up by the bullpen, but relievers throw far fewer innings and are protected from platoon advantages, making them far more difficult to analyze. Maybe I’ll work up the courage to address that in the future, but color me intimidated at this point in time)