Steven from FJB, noted that while Gio's HR numbers are low they may not be driven by a low GB%, but instead a particularly low (re: lucky) HR/FB percentage, helped in part by his home park. The early projections expect a increase in rate to say 9.3%. Given roughly the same number of FBs that would lead to about 4 more homers. Is this real?
Well, as far as I think, that's the worst case scenario. Gio's rank in HR/FB does follow pretty closely with his rank in GB%. (2010 13 out of 43 qualified AL pitchers in HR/FB, 13/43 in GB%; 2011 18/42 and 15/42). No, that isn't the best way to judge these things, but it shows that he isn't out of whack when it comes to these stats. It even suggests that he may be doing just right. Of course the home and road splits can't be ignored. In 2010 Gio had a HR/FB rate of 6.4% at home and 8.6% on the road, in 2011 the difference was 8.2% to 9.8%. Obviously the park was helping him. So what to believe?
Just to get an idea of how bad he could be in Nats park, I went ahead and pulled his worst FB% in the past 2 years (38.2% 2010 home), his worst balls in play (2.83 per inning 2011), and his worst HR/FB ration (the 9.8% noted above). Put that all together in a 200IP season and you get.... 21 homers. (assuming my back of the envelope calculations are right). So it seems like the projections are expecting the worst. (well the worst that could reasonably be expected.) All this is also figuring he won't pitch any different in a different park while his splits suggest he did allow more flyballs at home.
The short of it, for those that don't like fancy numbers, is that while his home park helps him with home runs it's not to a degree that Nats fan should worry about it. My expectations are that he will give up a couple more homers. There's just no way to deny that his home park helped him keep the ball in the park. But just 4 more would be about the limit of what I think could happen. There's virtually no chance in my mind that he suddenly gives up 25+ bombs and becomes a much worse pitcher because of that.