Cardinals news from a Sabermetric point of view

Miller, Rosenthal not fooling batters as much this year

One-fifth of the season is in the books, and the Cardinals are scuffling along with a .500 record, no thanks to their offense.  But with the third-best ERA and FIP in the league, Cardinals pitchers are keeping the team afloat.

However, the hurlers are not without their holes. In particular, Shelby Miller and Trevor Rosenthal have been a bit leaky this season, carrying xFIPs of 4.65 and 3.98, respectively. What’s going on with them?

Like all pitchers, Miller and Rosenthal need to achieve the dual goals of enticing batters to swing at balls and to not swing at strikes, as the great Greg Maddux was the master of doing. The Cardinal flamethrowers have a bit more room for error, since they throw hard, but the basic principle still applies.

We can actually measure this pitching philosophy by using swing data. That is, a pitcher’s out-of-zone swinging percentage (the higher the better) and his in-zone swinging percentage (the lower the better) can together give some idea of that Madduxian ideal. Simply subtracting O-Swing% from Z-Swing% yields a single useful number. Like ERA, the lower the better. Here’s how the Cardinal staff stacks up in what we’ll call the MAD Factor (after Monday’s game, in which both Miller and Rosenthal pitched):

# Name O-Swing% Z-Swing% MAD
1 Adam Wainwright 28.3% 61.6% .333
2 Carlos Martinez 36.1% 69.6% .335
3 Pat Neshek 32.9% 67.3% .344
4 Seth Maness 29.0% 66.7% .377
5 Michael Wacha 29.6% 68.3% .387
6 Randy Choate 29.4% 69.3% .399
7 Tyler Lyons 21.8% 63.2% .414
8 Lance Lynn 25.6% 67.9% .423
9 Kevin Siegrist 25.5% 68.5% .430
10 Keith Butler 26.5% 70.0% .435
11 Shelby Miller 20.7% 64.4% .437
12 Joe Kelly 20.8% 64.6% .438
13 Eric Fornataro 23.7% 70.3% .466
14 Trevor Rosenthal 18.2% 66.9% .487

As you can see, Miller and Rosenthal are among the worst on the staff so far. Rosenthal isn’t even getting batters to offer on pitches outside the zone 20% of the time, and Miller isn’t much better. As a result, batters are squaring up pitches in the zone more, leading to a higher line-drive rate (23.5% in Rosenthal’s case).

But it’s also leading to higher walk rates. Last year, Miller held his under 3.0 (2.96), while Rosenthal was a stingy 2.39). But in 2014, those rates have skyrocketed, at 5.26 and 5.28, respectively. Extra base runners will have negative consequences, especially for these guys, who aren’t ground ball specialists.

Fortunately, Miller and Rosenthal have good enough stuff — as in fastballs — to cover some of these bad trends. But despite a similar pitch mix to last year, Rosenthal may have lost a little velocity this season. As for Miller, he appears to be favoring his hard stuff more this year: He’s throwing his curveball four percentage points less than in 2013 and his change up 2.5 percentage points less. So it may be as simple as mixing it up a bit more.

We’ll keep an eye on the staff’s — and Miller’s and Rosenthal’s, in particular — MAD Factor.

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