Cleveland Guardians right-hander Triston McKenzie has been shut down due to a strain of his right teres major muscle (back of the shoulder) and could miss up to eight weeks, the team announced on Monday.

McKenzie left after just one inning of Sunday’s spring training game due to soreness and tightness in his right triceps and shoulder. He underwent an MRI on Monday morning, which confirmed the injury.

The Guardians say McKenzie will be shut down from throwing for at least two weeks and will be re-evaluated at that time.

McKenzie, 25, was a key piece of a Guardians’ rotation that helped propel them to a surprising playoff berth after winning the American League Central. McKenzie went 11-11 with a 2.96 ERA with over 190 innings pitched.

He was slated to start the Guardians’ second game of the season against the Seattle Mariners on Friday.