Koehler pitched to four batters Friday, retiring one. After he walked his second batter of the inning, Koehler was removed from the game, accompanied by athletic trainer Nate Lucero.
Koehler, 31, was on the disabled list for one month last season because of bursitis in his right shoulder.
Koehler split last season between the Miami Marlins and Toronto Blue Jays, posting a 7.42 earned-run average in 13 starts and a 3.00 ERA in 14 relief appearances.