The Red Sox traded Jed Lowrie and Kyle Weiland to the Astros for Mark Melancon.
Melancon is coming off his best year in his short career, with a 1.2 WAR. He isn't arbitration eligible, meaning he will make minimum wage for 2 more years. He threw 74.1 innings (more than all other years combined) in 2011, and had a -1.68 PE and -1.21 Adjusted PE as the Astros 9th inning man. Most "closers" (whatever the 9th inning man should be called) have much better PEs than this. He has a career SIERA of 3.26, gets lots of groundballs, and doesn't give up many homers.
Lowrie had a .3 WAR in 2011, and has a 3.8 WAR in 4 years, a .95 WAR average. He is arbitration eligible and is projected to make 1.2 million dollars according to MLB Trade Rumors. This is a very solid WASP of 1263 if Lowrie puts up his Average WAR. He is an under average fielding shortstop, and had a pretty poor fielding 2011. He has a career OBP of .324, 92 OPS +, and .267 Secondary Average. His Runs Created per game is 4.7, even though his Offensive Winning Percentage is .494. He walks above average, but homers below average. All things considered, Lowrie is a pretty average shortstop at a very reasonable salary.
Weiland has just 24.2 career major league innings. However, he had 24 AAA starts in 2011. He had a -1.71 PE and -1.57 Adjusted PE. Through the AAA metric, this translates to a .82 PE and .96 Adjusted PE. This is pretty solid for a starter. He didn't give up a bunch of homers (.7 HR/9IP), and had a reasonable walk rate.
I like this trade for the Astros. They trade away a decent cheap reliever, but they get a pitcher who should quickly be pretty good in the rotation, and a decent shortstop at a low price. This seems to be another example of late inning relievers being overvalued.