The Red Sox have acquired Jeremy Hermida from the Marlins for Hunter Jones and Jose Alvarez
Theoretically, Hermida could replace Jason Bay in left field, but only if the Sox make moves elsewhere to fill the void that would be left in the lineup. Hermida is a decent player with moderate power and pretty good speed, but he's nowhere near the same level as Bay is, offensively.
If the Red Sox pick up an elite shortstop or catcher, which would both be difficult at this point, then perhaps Hermida can start. Otherwise, he shouldn't be anything beyond a 4th outfielder.