Matt Carpenter filled his spot and the word was that he had suffered a left knee strain.
Beltran, who did not take batting practice prior to Wednesday's game, said he suffered the injury after he crossed first base.
He described the pain as feeling a pinch in the lower part of his quadriceps. Beltran said he waited a minute thinking he could ride out the pain and figured out fast it wasn't going away.
Beltran left the game Wednesday evening and traveled to a local hospital for an MRI. The MRI reportedly showed nothing new with the knee.
Manager Mike Matheny said the injury is not more of the same that he has been accustomed to dealing with for years.
"He's always managing, but not one spot in particular," Matheny said in a pre-game interview. "He stays on top of the strengthening that he needs and the rehab, just something he'll probably deal with as long as he plays. But it wasn't one particular spot that seemed to be bothering him. It just kind of grabbed him yesterday."
Regardless of the injury, Beltran didn't take Thursday off. Both he and Matheny said he would be available to pinch hit in Game 4 Thursday against the San Francisco Giants.
"I went to the cage, took some swings and it wasn't really bothering me, but probably today I'm a pinch hitter later in the game—I can be available to do that," Beltran told reporters.
Will Carlos Beltran play again in the 2012 Postseason?
He's not quite back to his old self, but he seemed confident this was a short-term issue.
"From the way I felt yesterday to the way I feel today is a lot better, but it's still sore," he said. "Hopefully one more day will give me a chance to get more treatment and hopefully try to be out there [Friday]."
Beltran has been a huge asset to the Cardinals in October, batting .400 in 9 games to date with three home runs, 6 RBI, 5 doubles and 6 walks.
He has the all-time highest batting average, .375 (42-for-112), among players with at least 100 postseason at-bats.
All quotes obtained firsthand.