A date and location of his start this week had yet to be determined by the team's coaching staff.
A mechanical flaw in Mulder's delivery still needed to be adjusted, and that may have played a role in the decision. After cruising through the first two innings on Friday, Mulder's arm slot suddenly fell and he was battered for four runs over the next two innings.
"He doesn't know why his arm dropped in the third inning," pitching coach Dave Duncan said. "He said he thought he could go out and pitch [in the Majors], but he didn't want to take a chance of that repeating itself, and I agreed. I'd rather see him pitch five innings of rehab and then go into a start for us."
Mulder said he was fully on board with the decision, admitting that his arm strength and command -- he threw only 39 of his 71 pitches for strikes -- were still far from where they needed to be to help a big league club.
"That's part of coming back, making sure you're ready," he said. "Why come back if I can only throw 70 pitches?"
Rolen still out:
Back spasms held Scott Rolen out of the Cardinals' lineup for a third straight day on Saturday.
Rolen took batting practice in the indoor cage Saturday afternoon, but the spasms have lingered, and La Russa has said the club will be cautious not to push him back.
Rolen is still day-to-day, but with an off-day Monday, look for the third baseman to be given Sunday off before making his return when St. Louis returns home on Tuesday.
Could Marquis be odd man out?
With the Cardinals holding such a tenuous perch atop the division, Duncan wasn't about to admit any given start is more significant than another.
"Every start is important this time of year," Duncan said.
Tell that to Jason Marquis, who may be facing as critical a start as they come on Sunday afternoon in Pittsburgh. His 5.82 ERA is highest among the league's regular starters and he is coming off a disastrous start Tuesday when he couldn't make it out of the third inning. After the start, La Russa said Marquis "was just out there firing."
But it was hardly anything new. Marquis, 27, has dropped four of his last five starts, not reaching the fifth inning during three of them. His spot in the rotation appears to be in jeopardy with Mulder's impending return.
So the Cardinals will clearly be keeping a keen eye on Marquis during his Sunday start, looking to make sure he is doing more than just firing.
"He's got to be more effective and consistent, get us deeper into the games than he's been getting us," Duncan said. "He's been making too many mistakes in the middle of the plate."
Pair of relievers given rest:
Relievers Josh Hancock and Adam Wainwright were not expected to be used on Saturday night, La Russa said.
Hancock tossed 1 1/3 innings in Friday night's loss and has pitched in four of the club's last seven games. La Russa will shy away from Wainwright until Sunday after Wainright's two-inning outing on Thursday in Cincinnati.
Braden Looper was available but not used Friday. The 31-year-old right-hander had been sidelined since Tuesday with back spasms.
"Just trying to keep MLB happy." -- LaRussa, on his club's inability to distance themselves from the NL Central logjam.
The Cardinals wore throwback St. Louis Stars jerseys on Saturday night as part of the Pirates' weekend celebration of the Steel City's rich Negro League history. ... Albert Pujols' trio of doubles on Friday night was the team's first three-double game since So Taguchi did it on Aug. 16, 2005.
The Cardinals will close out a weekend set with the Pirates on Sunday afternoon at PNC Park at 12:35 p.m. CT. Marquis (12-10, 5.82 ERA) will be opposed by Paul Maholm (4-10, 4.81 ERA).