Buchholz, 28, missed the entire 2009 season and most of 2010 due to Tommy John surgery. He returned in July to throw ten reasonably effective innings (4.50 ERA, 8.1 K/9) before landing on the disabled list with back stiffness. As Renck explains in a second tweet, Buchholz can choose to become a free agent if he goes unclaimed on waivers, however he would forfeit the $163K left on his contract by doing so.
Acquired from the Astros in the Jason Jennings trade four years ago, Buchholz pitched to a 2.17 ERA, 7.6 K/9, and 2.4 BB/9 in 66.1 innings of relief in 2008 before his elbow gave out. Given the dearth of quality relievers and the fact that Buchholz is under team control for another two seasons, there's a chance someone will roll the dice and place a claim.