By The Numbers: Groundball Rates

Mortensen has been a groundball pitcher.

Since the days of Rick Peterson as the team's pitching coach, the Oakland A's have favored pitchers with groundball tendencies. With that in mind, Nathaniel Stoltz takes a look at some of the A's minor league pitchers with intriguing groundball rates.

Stats good through Tuesday, May 18, 2010

When we look at minor league pitchers statistically, the stats most often cited are ERA, strikeouts and walks. Occasionally, you'll see homers allowed mentioned as well if that number is particularly high or low for the pitcher in question.

One number that comes up quite a bit more with major league pitchers than minor league pitchers is ground ball percentage, mainly because GB% is only offered for major leaguers by most sites. Places like Fangraphs don't incorporate batted-ball splits into their minor league data. To get to those numbers for minor leaguers, we have to go to minorleaguesplits.com.

So, here are some interesting batted-ball numbers (GB% in particular, but I'll mention some others as well) that I found when looking through Minor League Splits' data on the A's minor league pitchers.

NOTE: Pitchers with less than 20 innings pitched are not mentioned here, due to their small sample size. Pitchers not mentioned here with more than 20 IP generally have GB rates somewhere near the average (37-49%).

Clayton Mortensen has a reputation as a sinker-slider pitcher who gets a lot of ground balls, and although he's struggled this season, his groundball rate is a solid 50.9%. That's a bit under his career rate (53.2%), but still above average by quite a bit.

Mortensen has had issues with lefties in the past, but he's doing a nice job against them this season. Consider this table:

Batter Side

Groundball%

Line Drive%

Outfield Fly%

Infield Fly%

L

55.6

11.1

17.9

15.4

R

48.0

23.5

26.4

2.1


Grounders and popups are good, while liners and outfield flies are not. Clearly, Mortensen is inducing more pitcher-friendly contact against lefties than righties, which is good to see.

Like Mortensen, Triple-A hurlers Vince Mazzaro and Lenny DiNardo have reputations as groundball-heavy sinker guys, but neither has lived up to that this year. DiNardo has a 47.2 groundball percentage, which is a bit above average (average is 41-45%), but not enough to overcome his soft-tossing, contact-heavy ways.

Mazzaro posted just a 39.1% grounder rate with the A's last year, and is just at an average 42% rate for the River Cats. After posting a 57.6% grounder rate with Sacramento last year, it appears that Mazzaro lost some of his ability to generate grounders. Hopefully, he can get it back, as it's likely he'll be back in Oakland with Justin Duchscherer possibly out for the year.

One player known for his groundballing ways that is living up to them is Stockton reliever Paul Smyth. Smyth works from a low arm angle, which typically generated grounders by the bushel. A's fans have seen that from the groundballing exploits of Chad Bradford and Brad Ziegler in recent seasons.

Smyth has a 57.1% groundball rate, which is excellent. It's not surprising, given his arm angle, that he has a huge platoon split. Let's look at his batted-ball platoon splits like we did with Mortensen:

Batter Side

Groundball%

Line Drive%

Outfield Fly%

Infield Fly%

L

39.3

25.0

23.9

11.8

R

69.0

9.5

3.3

18.2


"Bad contact"—line drives and fly balls—makes up 48.9% of Smyth's batted balls against lefties, but just 12.8% of his contact against righties. That's about the most dramatic split you'll see.

Smyth looks like a future righty specialist.

Another pitcher with a notable platoon split is Midland lefthander Carlos Hernandez, who, like Smyth, has induced much more "good contact" against same-side batters.

Batter Side

Groundball%

Line Drive%

Outfield Fly%

Infield Fly%

L

61.0

2.4

22.3

14.3

R

41.7

25.0

29.9

3.4


Hernandez's "bad contact" split is 24.7% against lefties and 54.4% against righties, which is nearly as large as Smyth's split.

Hernandez's issues with liners against righties make his 2.27 ERA start a bit fluky, but the 23-year-old has completely shut lefties down, so he's got a future as a situational reliever if starting doesn't work out for him in the long run.

Another Midland lefthander who's making some noise getting grounders is Ben Hornbeck, who has a stellar 58.5% grounder rate, ahead of even Smyth. Thanks to his excellent changeup, Hornbeck doesn't have much of a platoon split. Hornbeck has improved his grounder rate by about 10% from last year, a step forward in a season where he's taken some steps backward in other areas, such as walks and strikeouts.

Sacramento reliever Mickey Storey has been a groundball pitcher against lefties this year (53.8%), while he becomes an extreme flyballer against righties (34.6%). He's striking out a ton of righties (14.66 K/9) while rarely fanning lefties (6.39 K/9). It could be that he elevates his fastball against righties in an attempt to strike out more batters high in the zone, while he simply looks to get lefties to hit his pitches on the ground.

Other notable groundballers in the A-ball levels of the A's system include Trey Barham (57.6%), Ian Krol (60.0% against fellow lefties, but just 41.4% against righties), Bo Schultz (59.8, including 66.0% against fellow righties) and Chris Mederos (63.2%).

On the extreme opposite end of the spectrum, Sacramento starter Graham Godfrey has a measly 32.8% grounder rate, although he's gotten away with it thus far, allowing just two homers in 41 innings. I wouldn't expect him to get that lucky all season, and unless he improves his command (34/26 K/BB ratio) or groundball rate, his 4.39 ERA is likely to rise.

To read more from Nathaniel, visit his blog at The Bleacher Report and chickenfriars.com.

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