Mujica, 28, was acquired from Miami in order to bolster a bullpen which has been one of the best lately. Mujica has a 4.38 ERA in 41 appearances this year.
"We're excited to have Mujica and I think he's going to be a nice fit," said Cards manger Mike Matheny. "We've obviously seen him a lot through Spring Training and through the season. The guy is going to bring in some experience and help out some of our young pitchers down there."
Neither St. Louis starter Jake Westbrook nor Colorado starter Drew Pomeranz have faced each other's club this season. Westbrook has won two straight outings and was 3-2 with a 3.18 ERA in July. He last went fewer than six innings in a start on June 3 against the Mets, when he allowed five runs over five innings.
Pomeranz is 1-6 and has fell victim to a lack of run support in a couple of those losses. In his most recent outing, Pomeranz allowed three runs over 5 1/3 innings in a 3-0 loss to the Reds on Friday.
Cardinals: Garcia's next rehab start slated for Saturday
Lefty Jaime Garcia will make a rehab start at Double-A Springfield on Saturday. Garcia, who's been on the disabled list since June 6 with left shoulder impingement, threw 2 1/3 shutout innings for the Gulf Coast League Cardinals on Monday.
Garcia is expected to throw 60-70 pitches, and is likely to need two to three more starts before the Cardinals will consider returning him to the rotation.
Shortstop Rafael Furcal has missed three straight games with lower back stiffness. Furcal did not swing a bat over the weekend, but did taking batting practice on Tuesday. His availability for Wednesday's game is up in the air.
Rockies: Friedrich's next start pushed to Sunday
Rookie left-hander Christian Friedrich, originally scheduled to start Thursday against the Cardinals, will instead start Sunday against the Giants. The move comes in hopes of getting Friedrich over the midseason hurdle.
The 25-year-old Friedrich is 5-8 with a 6.17 ERA and has given up 14 earned runs in his last 14 innings.
Center fielder Dexter Fowler was scratched from Tuesday's lineup with flu-like symptoms. Fowler is second among National League leadoff hitters with a .326 average since moving to the top spot May 28.
Eric Young Jr. started in center in Fowler's place, and went 3-for-5 with a double and a pair of runs scored.
Michael Cuddyer has nearly half of Colorado's career at-bats against Westbrook. Cuddyer is a career .346 (9-for-26) hitter against Westbrook, with a double and five RBIs.
Rockies rookie shortstop Josh Rutledge went 2-for-5 with a homer and a double on Tuesday, giving him eight multi-hit games since making his debut on July 13. Rutledge is batting .381 in 16 games over that span.
Cards closer Jason Motte threw 27 pitches in a scoreless ninth Tuesday, the most pitches he'd thrown since hurling 29 against the Royals on June 17.