Bay is hitting .308/.406/.508 at Citi Field, but just .246/.333/.333 on the road. He has twice as many extra base hits in front of those frustrated fans as he does in front of ambivalent road crowds. If he was hitting as well away from New York as he was at home, we wouldn’t be having this discussion.
The same is true of Vazquez, though not to the same extent. He is posting a 4.48 xFIP at home versus 4.72 on the road, with neither number representing his previous abilities. The same was true in 2004, when Vazquez pitched better in Yankee Stadium than he did away from the Bronx.
Sometimes a slump is just a slump. Guys slump in New York just like they do in Milwaukee, San Diego, or St. Louis. Perhaps we should avoid slagging a guy’s intestinal fortitude when he is performing better in front of the same fans and media that are supposed to be scaring him into a slump.
The most famous "can't handle the New York pressure" Yankee is probably Ed Whitson.
Yet oddly (or not), he too actually did better in New York than on the road. In 1985, his first season with the Yankees, he posted a 4.08 ERA (and an excellent strikeout-to-walk ratio) in a dozen Yankee Stadium starts, but didn't pitch nearly as well in 18 road starts.
In '86, Whitson started only four games (and relieved in 10) before getting traded to the Padres, his previous team (and for whom he continued to struggle, not really finding his game again until 1988).
I don't mean to suggest that Whitson wasn't rattled by the pressure in New York. He's admitted as much, particularly in the first couple of months of his first season there.
I don't mean to suggest that different players don't react in different ways to different environments. They are not (as I've been reminded a few times over the years) robots. But sometimes a slump is just a slump. Or an injury. Or elementary regression. And I find particularly laughable the notion that Jason Bay can't handle New York ... as if there's not immense pressure to perform in Boston, where Bay just came off one of his best seasons.