FanGraphs has analyzed how Jason Bay should fare in Citifield, based off of how he did at Fenway last season.
“Baseball-Reference’s Play Index Tool gives the option of taking a batter’s line and adjusting it, based on the offensive level of the league (NL or AL) and the run scoring environment of the ball park. According to the Play Index Tool, here’s what Bay’s 2009 season would have looked like, had it occurred in Citi Field:
Actual: .267/.384/.537, .269 ISO
Adjusted: .265/.380/.535, .270 ISO
The net impact doesn’t appear to be huge. On one hand, Bay is going from a clear hitter’s venue to a park that played as pitcher-friendly in 2009. But on the other, he’s moving back to the NL. Derek Carty of The Hardball Times showed last off-season that batters going from the AL to the NL receive a slight boost in contact rate, home run per fly ball percentage, singles and doubles.”
Overall, I don’t think there will be much of a difference in his offensive production. Mets officials felt that Bay fit better at Citifield than Holliday did and I would generally agree that Bay should fit in nicely at Citifield