Just a week after returning to the Mets’ rotation after elbow surgery, relief pitcher and Crozet resident Billy Wagner agreed to be traded this afternoon to the Boston Red Sox, who’ll pick up the remainder of his $10.5 million salary and allow him to become a free agent in 2010. The move puts the 38-year old Wagner in the thick of the American League Wild Card race, with Boston just 1.5 games ahead of the Texas Rangers. Boston most likely wants the hard-throwing lefty to balance out their bullpen, which only has one left-handed relief pitcher (Hideki Okajima) on the active roster.  During Wagner’s return start last Thursday, he pitched a scoreless inning against the Braves and struck out two, a performance he repeated on Monday against the Phillies.