Morse is one of those guys I'd love to have a measure of velocity of his bat. that data is still propietary to Hit/fx. I think it might explain how a guy that slow can consistently have a fast guy average on balls in play.
He's interesting in that, while he's been around since 2005, he had that long period of going back to the minors. Something like 70% of his PAs are from 2010 - 2011, when he was big and slow, while about 20% are in his first call up when he was smaller and still a SS. In his 3 seasons with the most PAs, he's always hit around 45% GBs. His first call up, he had an unsustainable 25% LD rate, and he was less filled out and slow, so that combo explains his .341 BABIP that year. In 2010, he had a low LD rate (16%), and most of the missing LDs shifted to FB. His BABIP was only .330, which is still high for a big slow guy but lowest of his 3 seasons with the most PAS. Last year, he had a more normal rate of liners (19.5%), and his BABIP returned to .344, near his career norm. It'll take more work to get into the publicly-available numbers to figure out where his "luck" is coming from, but I'm guessing some of it is the lack of a book on postioning OFs for flies, and some of it is staying up the middle on his GBs, and some of it is velocity off the bat.