Manager Mike Matheny said that Robinson sustained the injury sliding back to first base on a pickoff attempt in Game 1 of Tuesday's doubleheader. Robinson had reached base with a walk in the pinch-hit appearance and ended the inning stranded at third. He did not appear in the second game.
Robinson, like Molina, flew to St. Louis on Wednesday for an MRI, which showed no structural damage. General manager John Mozeliak said that Robinson may not need the full 15 days to recover, but the team did not want to play short a bench player and backup center fielder for even a few days.
"I think the best thing is to give him a couple weeks to get recovered," Mozeliak said. "I'm hopeful it won't take him that long, but I just didn't feel comfortable, especially with our schedule, to go short."
The extra center fielder is now Chambers, who will be making his first appearance in the Majors this season. In 98 games with Triple-A Memphis, he batted .252 with a .338 on-base percentage and 15 stolen bases. After a four-hit game on Tuesday, he is 29-for-82 in July.
Peterson gives the Cardinals the right-handed bat off the bench that the team loses with Robinson out. Peterson returns to the big league club after only a few days away. He was optioned to Triple-A on Saturday when Matt Holliday returned from injury but did not have to stay the requisite 10 days, because the Cardinals made another DL move.
Peterson, who has hit a Pacific Coast League-high 23 home runs, went 1-for-7 during his previous stint with the team.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.