Even though Uehara has stepped in well as the closer, I feel the Sox need another reliever. That being said, I doubt giving up prospects is a Ben Cherington thing. It's not worth to rid of Bogearts or Cecchini to get a starter in this market, either.
The only upgrades that the Red Sox need right now are in the pitching. Even if Buchholz comes back, we may have another injury bug in the works that can pop out any time this season. I suggest giving up a mid-level prospect like Holt due to the amount of depth we have at first base (and possibly another lower-level C prospect) in order to receive someone like Travis Wood. He's been a solid pitcher for the Cubs so far, he keeps ground ball rates high and walk rates low, at 2.6 per 9 IP. He doesn't strike out too many batters at 6.5 per 9 IP this year, but he's known to be a smart guy. His off-speed stuff has a lot of movement; the only problem is, I don't know if he's on the trading block.