Mulder
The left-hander, coming back from two shoulder operations, made three starts last September and was 0-3 with a 12.27 ERA.
"We will see how it goes," said Mulder, who was 0-3 with a 13.50 ERA in three rehabilitation starts for Triple-A Memphis.
He has made 202 major league appearances, all starts, going 103-60.
"Based on his experience, I don't think anybody is going to be comfortable hitting against him," said manager Tony La Russa.
To make room for Mulder, the Cardinals optioned pitcher Mike Parisi to Triple-A Memphis.
St. Louis had hoped Mulder could start Saturday against the Royals but his back felt stiff during a rehab start Monday and he had a so-so bullpen session on Thursday.
Mulder will temporarily fill the void left by Randy Flores, who has left ankle tendinitis and on Thursday became the seventh Cardinals pitcher on the DL. Flores had been the second left-handed reliever alongside Ron Villone.
"I'm definitely excited. Obviously, there's a need for it," Mulder said. "I've always liked facing lefties."
Jason Isringhausen was unavailable on Friday night and could be headed back to the disabled list after feeling a pop in his knee while stretching in the dugout during Thursday's game against the Tigers.
"There's clearly some reason for concern at this point," general manager John Mozeliak said. "It's frustrating, that's for sure. It was nice to see the success he was starting to have, and I'm very hopeful that this isn't a serious injury."
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