"Right now we have very limited information," manager Jeff Banister said. "The information I have is it's a calf strain and he had an MRI. We'll see."
Choo injured the muscle doing his lower leg preparation work during batting practice.
"We felt it was bad enough not to push it," Banister said. "We weren't going to take any risks."
Ryan Rua started in right field for the Rangers. The injury came one day after the Rangers designated outfielder Justin Ruggiano for assignment. Nomar Mazara, who is at Triple-A Round Rock, is the only outfielder on the 40-man roster not currently in the big leagues.
T.R. Sullivan is a reporter for MLB.com. Follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.