The first baseman was placed on the 15-day disabled list on Wednesday with a strained left calf. Pujols originally sustained the injury on June 3 in Washington, but aggravated it Tuesday night breaking from the batter's box on a grounder.
As expected, Chris Duncan was called up from Triple-A Memphis and will start in Pujols' place at first base. Duncan will bat sixth, while Ryan Ludwick will take Pujols' spot at third in the order.
Pujols underwent an MRI with team medical supervisor Dr. George Paletta on Wednesday in St. Louis. The MRI revealed Pujols had sustained a strain between a Grade I and Grade II. A Grade I strain means the muscle is stretched, causing very minor tears in the muscle fibers. A Grade II strain indicates partial tearing of the muscle fibers, while a Grade III strain indicates a complete tear.
A full recovery from a Grade II strain typically takes between five and eight weeks.
Pujols will begin physical therapy within the next three days, and though he will be out a minimum of three weeks and has been known to play when he's less than 100 percent, Cardinals manager Tony La Russa said he wants Pujols back at full strength before he makes his return.
After hitting a grounder to first base in the seventh inning against the Reds on Tuesday, Pujols broke for first, but pulled up just outside the batter's box and fell to the ground. Reluctant to put any weight on the leg and in obvious pain, he had to be helped off the field by teammates.
"The games still count," La Russa said. "It's not like there's a void there. Someone's going to play and take at-bats. Nobody's going to give us any extra points or anything."
Indeed they won't, but the Cardinals will be scrounging for any help they can get after a devastating road trip. In addition to Pujols, starting pitcher Adam Wainwright sprained his right middle finger against the Astros on Saturday. Wainwright was sent to the 15-day DL on Tuesday.
La Russa said Duncan would have probably been called up soon anyway, though it would have been to play in the outfield. Duncan, a natural first baseman, was optioned to Memphis on May 30 to iron out his hitting troubles.
Since sustaining a hernia at the end of July in 2007, Duncan has hit just .217 and slugged .323 with five home runs in 217 at-bats. In seven games at Memphis, he hit .160 with four hits and three RBIs, but Duncan said he had been seeing the ball much better and was ready to be back with the Cardinals.
"It's good to be back, but it's under bad circumstances with Albert," Duncan said. "It's tough that a player of that caliber is out. I'm going to do anything I can to help."
Brandon Harris is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.