Friday, August 19, 2011


Mariano Rivera strikeout rate, walks, and ERA holding up

This article gives some perspective to Rivera's current stats like K's, BB's, ERA, velocity, and pitch values:

8/18/11, "Any worries about Mariano Rivera should be quickly dismissed," FantasyWindup, USA Today blogs, by FantasyPros911, P. DiCaprio

"After a few dicey performances many fantasy owners are asking whether Mariano Rivera is nearing the end of his illustrious career. If he is, there is no evidence of it, as we will see below. If anything, his skill set shows little or no erosion.

Strikeouts - His strikeout rate is up to 8.04 K/9, well above last year's mediocre 6.75 showing. The 2011 figure is down from his peak, but well within his expected range of strikeout rates. Rivera has struck out fewer batters per nine in nine of his 17 seasons.

Walks - His walk rate has gotten even better as he has aged. He has walked fewer than two batters per nine innings in each of the last six seasons, twice walking fewer than one batter per nine. The two seasons? 2008 and 2011, when Rivera walked 0.76 and 0.96 batters per nine. So, 2011 represents his second best control season.

ERA - His current ERA is 2.30, plenty good for anyone. But is it a product of his skill, luck or something else? One way to tell is to look at the more advanced metrics. So let's look at FIP and xFIP (both from and xERA (from -- three of the more useful ERA estimators:

Actual ERA: 2.30
FIP (Fielding Independent Pitching): 2.38
xFIP (Expected FIP): 2.70
xERA (Expected ERA): 2.84

These metrics purport to distill a pitcher's ERA into its component parts to see if his ERA is likely to regress to a mean. Here Rivera's ERA is clearly not subject to anything other than a tiny regression.

Pitch Values - tracks pitcher velocity and determines a run value for each pitch type. Mariano's 92.1 average fastball velocity is almost exactly the same as in 2010 (92.2). But we all know his fastball is not his bread and butter. In fact he has thrown it only 11% of the time, by far a career low, aside from 2009, and part of a continued reliance on the cutter as he has aged.

As it turns out he has lost a step on his cutter in terms of run value. Mariano has seen a three-year decline in his cutter run value: 25.2 in 2008, 19.8 in 2009, 16.7 in 2010 and 8.0 so far this year. With roughly a quarter of the season left, we can prorate 2011 to 10.0 by the end of the season. This looks like a big decline, and it is.

The decline is from his career high. Prior to 2008 his cutter run value was 12.2 in 2006 and 11.5 in 2007, seasons in which he had fewer strikeouts, but relied on his fastball much more often.

Of course we expect some decline in a 41-year-old pitcher. But Mariano is still rock solid for fantasy players. And if you do not agree, how many closers would you take ahead of him?

-- Patrick DiCaprio, Fantasy911Pros

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