http://fullcount.weei.com/sports/boston/baseball/red-sox/2015/03/21/morning-fort-joe-kelly-not-making-scheduled-start-shane-victorino-abandons-switch-hitting/
John Farrell:
“Even though he came out of his bullpen the other day with no issue, still at 70 percent, which might be a normal bullpen, we just want to get him up to normal game intensity, but not in a game setting,” Farrell said. “Maybe it’s a little precautionary, but it’s something I feel like he walked off the mound in a middle of a start and we’ll take that extended bullpen tomorrow with an eye on him making his normal start next Friday. … Not a setback whatsoever, just an intermediary step towards getting to game speed.”
I don't see anything about "healing slower".