Right-handed pitcher Alex Cobb, the Cleveland Guardians’ Game 1 starter in the American League Championship Series, is done for the postseason after aggravating a back injury on Monday night.

MLB approved Cleveland’s roster substitution, which adds right-hander Ben Lively to the ALCS roster and removes Cobb. By rule, Cobb is ineligible for the World Series should the Guardians advance.

The Guardians acquired Cobb, 37, from the San Francisco Giants at the trade deadline and he didn’t make his season debut until Aug. 9 after recovering from offseason hip surgery. Due to a blister and nail fracture on his pitching hand, Cobb only appeared in three regular-season games for Cleveland.

Cobb left in the third inning of Monday night’s 5-2 loss to the New York Yankees. He threw 65 pitches in 2 2/3 innings and yielded three runs on five hits and three walks, striking out three. Manager Stephen Vogt said postgame that Cobb was experiencing hip tendinitis and a back spasm.

Lively, 32, was in Cleveland’s rotation throughout the season and went 13-10 in a career-high 29 starts, pitching to a 3.81 ERA and striking out a career-best 118 batters with 49 walks in 151 innings. He led the Guardians in wins.

The Guardians and Yankees play Game 2 on Tuesday night in New York before the series shifts to Cleveland for Games 3-5.