Pop-Quiz: Which pitcher would you project for a better ERA the rest of the season, assuming each sustains their current skill-set?

Pitcher A: 5.6 K/9, 1.5 BB/9, 42% GB%

Pitcher B: 5.6 K/9, 2.4 BB/9, 45% GB%

Both pitchers play in the same division, in the same league and their home ballparks aren’t much of a factor.

If you answered something like “they should post similar ERAs because Pitcher B’s higher GB% offsets his higher BB/9″, then you’d be in complete agreement with me. Judging by the title of this article, you must have known one of the pitchers was Jeremy Guthrie. He would be Pitcher B. Who is Pitcher A? None other than the Rays’ Andy Sonnanstine, the minimally valued mixed league pitcher. If you owned Guthrie and were offered Sonnanstine, you would probably laugh at the other owner. With a sparkling 3.18 ERA and 1.15 WHIP, following a breakout ‘07 season that saw him post a 3.70 ERA and 1.21 WHIP, it would appear on the surface that Guthrie is becoming one of the best pitcher’s in the AL. Not so fast…

Last year, Guthrie suffered quite a regression post-All Star Break to the tune of a 5.03 ERA and 1.62 WHIP. This year, however, he’s so far avoided the 2nd half slump by posting a 2.20 ERA and 1.02 WHIP over 41 innings. If we mosey on over to The Hardball Times to check on his xFIP, we see a 4.37 mark, way above his current 3.18 ERA. Furthermore, he ranks 9th in all of baseball in FIP-ERA differential, with a FIP ERA 0.98 higher than his actual. What these metrics suggest is that his skill set is as average, vanilla and boring as you could get, and in fact, is right there with Sonnanstine’s who sports a 4.25 xFIP this year.

So how is Guthrie outperforming his xFIP so dramatically you ask? The .263 BABIP certainly has a lot to do with it, and that ranks 11th in all of baseball. And what about his 77.5% strand rate that ranks 8th in all of baseball? When you combine those two with a slightly lower than league average 9.1% HR/F, you could clearly see how he’s been able to sustain such “success”. Of course it’s possible that his low BABIP is the result of exceptional movement on his pitches, but I’m not a PITCHf/x guru unfortunately, so I can’t make that determination. Or then again, that explanation could just be another example of the Texas Sharpshooter Fallacy.

The verdict here is that given the very mediocre skills Guthrie possesses, the percentage play is to expect a regression in his ERA, possibly enough so that it wipes out almost all of his mixed league value. I would not be surprised at all if his ERA is over 4 the rest of the year, and even for the 2009 season. In reality, matching Sonnanstine’s ratios are a much stronger possibility than anyone might realize.

Questions, comments, criticisms, praise, expert league invitations? Email me at FBGeneralsMike@gmail.com.