The Pirates have signed or re-signed three pitchers to minor league deals: Neal Cotts, Brian Burres and Tyler Yates. You're all familiar with Yates, and while I'd personally rather have the organization just wash their hands of him, a minor league deal is potentially harmless, at least.
Cotts is the most interesting of the trio. He's a 29-year-old lefty reliever with a spotty record at the major league level, but he has posted good numbers at AAA the past two years. He had an amazing season in 2005 with the White Sox during which he threw almost entirely 90 MPH fastballs, but it seemed as though hitters adjusted to that strategy the following year. (It's also possible Cotts simply ran out of luck; he's always been a flyball pitcher, but he somehow only allowed one homer in 2005 before allowing 12 in 2006.) He ended up with the Cubs in 2007 and concentrated more on throwing secondary pitches, with little success. His fastball is probably his best pitch (even though he doesn't throw hard), and he doesn't seem to have much of a slider, so he probably shouldn't be used as a LOOGY. It might be worthwhile to have Cotts go back to throwing about 80% fastballs to see if he can catch lightning in a bottle twice, because that's what briefly worked for him in the American League. Unfortunately, he had Tommy John surgery last July, so he probably won't be of much use until June at least.
Burres is a little like a lefty version of Virgil Vasquez--he mostly just chucks 87 MPH fastballs, mixes in some secondary stuff, and hopes for the best. Actually, his fastball is even slower than Vasquez's. That can work, to a limited degree, in AAA, but as with Vasquez last year, it probably won't do for the Pirates to have Burres in the majors. Like Vasquez, Burres' main virtue is that he can start--he started 39 games for the Orioles between 2007 and 2008.