Tuesday, April 04, 2006

Rick Helling and HR Rates

In limited work last year, Helling put up an unexpected 2.39 ERA while filling in for an injured Ben Sheets. Could the 35 year old be experiencing a late career resurgence? Let's dig into the numbers:

Rick Helling, 2005
IP:     49.0
ERA: 2.39
FIP: 3.04
xFIP: 4.74
LOB%: 81.9%
For an explanation of those metrics see this post.

That 81.9% LOB% is simply not sustainable. A pitcher would have to carry about a 1.25 ERA to justify such a low LOB%. Helling's xFIP shows that he got extremely lucky with his HRs last year. How lucky? Here's what his HR/FB% has been in the last 3 years he's pitched:
YEAR   HR/FB%
2002 12.1%
2003 15.0%
2005 2.9%
-------------
Career 10.7%
The NL average last year was 12%. His 2005 HR/FB% was flukishly good. As hardballtimes.com says, "Research has shown that about 11% to 12% of outfield flies are hit for home runs. For pitchers, significant variations from 11% are probably the result of "luck...". But his career HR/FB% suggests he should still have a pretty decent HR/IP rate (he doesn't). It turns out that the problem isn't his HR/FB%, but rather his GB/FB ratio.

To illustrate this, let's compare Helling to a list of players with some of the best HR/9 numbers in recent years:
                HR/9   HR/FB   GB/FB
M. Rivera .47 5.8% 1.51
Kevin Brown .57 9.3% 2.62
Greg Maddux .61 9.4% 2.37
Roger Clemens .66 9.3% 1.45
Tom Glavine .68 7.4% 1.45
Pedro Martinez .69 8.1% 1.09
Rick Helling 1.45 10.7% 0.67
Most guys, like Kevin Brown or Greg Maddux, sustain a low HR/9 by being extreme ground ball pitchers. Rivera is a freak of nature. His HR/FB% of 5.8% blows everyone else out of the water. I'd be tempted to guess that that's the lowest HR/FB% of any pitcher who's accumulated any substantial amount of innings. Helling is such an extreme fly ball pitcher that he could never have good HR numbers. His GB/FB rate is just too low.

Using his career average HR/FB, he "should" have given up 8 HRs instead of his actual 2 in 2005. Those 6 HRs saved were worth about 8 runs and 1.4 points off his ERA. That would still have given him a decent 3.9 ERA, but having faced only 199 batters in 2005, I'd be skeptical of drawing any conclusions from his 2005 stats. Claiming that Helling's 2.9 HR/FB% and 2.39 ERA wasn't a fluke is like saying a career pinch hitter batting .425 in 135 ABs wasn't a fluke. Crazy numbers can fall out of small samples.

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