The Pirates have acquired J.A. Happ from the Mariners for Adrian Sampson.
Happ is a free agent after the season, so the Pirates presumably traded for him with the idea that he can provide help now. He's been a starter in the big leagues almost exclusively, but we'll see if the Pirates want to use him in that role or perhaps as some sort of lefty-long-reliever-slash-insurance-policy. It could be that A.J. Burnett or someone else will head to the disabled list for awhile.
Happ has a 4.64 ERA this year; his peripherals suggest he's been somewhat better than that, but he's long been a low-fours ERA guy on true talent. Maybe he'll be a bit better than that now that he's back in the National League, but I wouldn't expect anything transcendent from him. This looks like a pure depth move, which is interesting, because you might look at Sampson's numbers and wonder if he might be able to provide that same kind of depth. The Pirates are giving up six-plus years of control of Sampson to get two months of a pitcher who looks somewhat similar in capability.
Sampson has struggled recently, though, and the Pirates know him better than anyone. More to the point, he's a back-of-the-rotation type and doesn't have much upside beyond that, and if the Bucs think Happ is even a little bit better right now, it's probably worth it. Sampson is a nice pitcher to have around, but it's not worth sweating too much if you lose him. The Pirates also would have had to add him to their 40-man roster after the season.
Anyway, it will be interesting to see how Happ and Michael Morse fit on the Pirates' roster. That will give us a bit more information about how the Pirates plan to use them.