Another miserable performance Thursday earned troubled St. Louis Cardinals reliever Mitchell Boggs another trip to Class AAA Memphis.

Boggs, who allowed two ninth-inning runs Thursday in the Cardinals' 4-2 loss to Kansas City, was optioned Friday to Memphis and was replaced by Keith Butler.

Butler, 24, will wear No. 65. He becomes the 11th rookie to join the Cardinals this season and will become the 11th pitcher age 25 or younger to toil for St. Louis.

Butler was 0-0 with a 0.66 ERA in 13 games and 13 2/3 innings at Class AA Springfield. He had two walks and 21 strikeouts and stymied hitters to a paltry .163 average. He opened the season at Class AAA Memphis, where he was 0-1 with a 9.53 ERA in seven games and 5 2/3 innings.

The 6-foot, 170-pound Butler was chosen by St. Louis in the 24th round of the 2009 draft.

Boggs was optioned to Mempis on May 2 and recalled by the Cardinals on May 19, but he has struggled mightily this season with an 0-2 record and 10.43 ERA.

With Edward Mujica unavailable Thursday, Cardinals manager Mike Matheny entrusted Boggs with a 2-1 lead in the ninth, but the Royals' Jeff Francoeur sent Boggs' first pitch over the wall in left for a game-tying homer.