Span strained the right side of his collarbone while diving to make a catch against Tampa Bay on Aug. 12. He has missed 13 of the 17 games since the injury, with Ben Revere taking over the bulk of the work in center. The move is retroactive to Tuesday.
Span is hitting .286 with three homers and 35 RBIs this season.
The Twins say they will announce a corresponding roster move when they arrive in Kansas City on Friday.
Span says he was surprised by the decision. But he also says he knows it's "not fair to the team" to keep coming in and scratching himself from the lineup.