I just looked up his fangraphs. No idea how he was the one guy last year to out perform his FIP and xERA by that much, but it sure makes a solid regression case, and the projections seem to agree.
It goes to the Sox only being willing to take hom back if he was being paid less than Martin Maldanado with more recent information than anyone else in baseball. They don't think a lot of him or they would have paid him what his stats say.