The St. Louis Cardinals are sending Justin Masterson to the bullpen.

Masterson has struggled since St. Louis acquired him from the Cleveland Indians in July. He was scheduled to start on Thursday.

"We've got him in that mindset already," Mike Matheny said of a relief role. "When he'll be actually available to go is still up in the air."

Masterson has made six starts for the Cardinals, going 2-3 with a 7.90 ERA.