The move doesn't come as a surprise, as the right-hander missed the entire 2012 season after undergoing Tommy John surgery on his elbow in April. He's set to become a free agent on Friday night at 11 CT.
General manager Terry Ryan has stated an interest in bringing back Baker on a new deal, however, as left-hander Scott Diamond is the only pitcher with a guaranteed spot in the rotation next season.
Baker indicated at the end of the season that he'd be interested in returning and that he's hopeful he'll be healthy and ready to go in time for Spring Training.
Baker, 31, has spent his entire career with the Twins, posting a 4.15 ERA with 770 strikeouts and 224 walks in 958 innings. He had his best season in '11, with a 3.14 ERA, but threw just 134 2/3 innings while dealing with elbow issues in the second half of the season.
The Twins now have three impending free agents, as Carl Pavano is also a free agent and the club declined Matt Capps' $6 million option on Wednesday.