One of the key points that the pro-Washburn camp is leaning on is that, if ERA is any indication, the guy has been a markedly better pitcher away from Edison Field, to the tune of a 127-point improvement for his career. The argument is that, by keeping Washburn out of Anaheim, he'll be considerably more effective at run prevention, going a long way towards earning his contract.
I thought I'd take a closer look at this, scrolling through Washburn's last four seasons (because the ESPN game logs only go back to 2002). Observe:
Washburn At Home, 2002-2005:
RA: 4.71
K%: 14.3
BB%: 6.5
GB/FB: 0.78
Washburn On The Road, 2002-2005:
RA: 3.36
K%: 13.7
BB%: 6.9
GB/FB: 0.76
Strikeouts, walks, and groundballs (or flyballs, but it's the same idea) are the three things that pitchers can consistently control on a year-to-year basis, and all three of them have actually been a little worse away from Edison Field over the past four years. Not significantly so, but the gap is there, and it's real. See for yourself.
So the question becomes, why the lower RA? If Washburn's peripherals are no better on the road than they are at home, he should be giving up the same amount of runs regardless of where he's pitching, right?
Washburn At Home, 2002-2005:
HR/outfield fly rate: 11.3%
Washburn On The Road, 2002-2005:
HR/outfield fly rate: 8.9%
(Note that these are estimates, based on a 12% tendency for Washburn's flyballs allowed to remain in the infield.)
Okay, there it is. Where Washburn allows a normal number of flyballs to clear the fence at home (the standard rate is about 11%, according to the Hardball Times), he puts up a much better rate on the road, leading to the reduced RA. It's remarkable what can happen when you don't allow too many homers.
So is it a repeatable skill? Unlikely, because (A), he'd be the first known exception to the rule in baseball, and because (B), if it were, then you'd see him putting up the same kind of rate at home, because it's not like Anaheim is a homer-friendly environment or anything. I see no reason to believe that Jarrod Washburn is the sole owner of a mysterious ability to keep flyballs in the yard.
How would one go about explaining this difference? To be honest, I'm not really sure, although it might have something to do with the fact that two of the other three stadiums in his division are incredibly friendly to pitchers. I think the more likely answer, though, is that Washburn is simply a larger-sample statistical fluke.
You can do this binomially, if you wish. Over a sample of 552 outfield flyballs (my Washburn-on-the-road data for 2002-2005), an average pitcher would allow about 11% of them to clear the fence, for an n value of 61. The probability of a guy allowing 49 (Washburn's total) or fewer comes out to 6% - in other words, for every 100 pitchers you look at, six of them can be expected to have rates similar to Washburn's. For the sake of comparison, Richie Sexson went deep in exactly 6% of his plate appearances last season, so it's not like this percentage is so small that it's difficult to believe.
The key thing to realize here is that the rates of those six pitchers are not, statistically speaking, significantly different than the mean. They are to be expected within the data pool, and only begin to disappear as the size of your sample increases.
I can't say with absolute certainty that Jarrod Washburn is one of these 6% of pitchers, particularly because the trend appears to date back to before 2002 (which I can't really quantify, given the limits of ESPN player profiles). However, I think it's easier to believe than the theory that Washburn suddenly develops a unique ability to turn flyballs into outs at a greater rate when he gets out of southern California. God knows he's not pitching any differently, if his strikeouts, walks, and GB/FB ratio are any indication.
Jarrod Washburn may turn out to be a true anomaly, one of the first of his kind. And he'd better be, because the only way a guy with his age and statistical profile deserves an expensive four-year contract is by practicing magic. Cross your fingers.