The Pirates are a "fast-emerging dark horse" in the bidding to acquire Jon Lester from the Red Sox, Jeff Passan and Tim Brown write. Josh Bell is apparently a central piece in the talks.
I would take all this with a grain of salt. There isn't any recent precedent for the Pirates trading a top prospect like this for a pure rental. The Red Sox also want Lester to return next year and probably won't give him up at all cheaply. Trading Bell for a veteran might make more sense if there were years of control involved, but Lester is a free agent after the season, and there's virtually no chance the Pirates would retain him.
That said, I suppose this isn't impossible. The Brewers traded for C.C. Sabathia as a rental player several years ago and he dominated for them. The package the Brewers gave up centered around Matt LaPorta, who was a bust. Michael Brantley was also in that deal, but I don't think the Brewers regret it in the least. I'm not sure trading Josh Bell plus other prospects for Lester would be wise, but it would be refreshing, in a way, as a signal that the Pirates can bid for top talent.
The Dodgers are also reportedly interested in Lester.
UPDATE: Rob Biertempfel writes that the Pirates would have to give up Bell plus another top prospect, such as Tyler Glasnow. That seems crazy to me.