As a Phillies fan, I almost feel like I should apologize to Rays' fans for the year Pat Burrell is having for the Rays this year. Clearly what showed up in Tampa Bay fell far short of what was advertised.
He did this once early in his Phillies' career. After having a career-high 37 homeruns in 2002, Burrell proceeded to have a terrible year where he hit around.190 or most of the next season and rallied to finish at a slightly less bleak .210. He came back to have some pretty good seasons since then, until his current troubles.
Many other hitters who spent all their career in one league have had terrible first years after switching to the other league. Often they have bounce back years in their second year in the new league after making adjustments. Their second years come back close to their career norms in batting average and productivity. (Ted Simmons in the early '80s, going from St.Louis-NL to Milwaukee when the Brewers were still in the American League, is a classic example. A .290s career hitter with the Cardinals, he hit about 100 points higher his second year in his new league after stinking up the joint in his first year with the Brewers).
I think that you might see signs of improvement late this season from Burrell and I think he'll have a good year next year in Tampa, if Rays' fans don't run him out of town first.