"I tried to play through it, but it's getting worse," Molina said after the Cards' 6-0 loss to the Pirates. "The smart thing is to take time off and try to fix it. I've been playing through that since June. Like anybody else, I am one of the guys who wants to be on the field playing. But right now I need time."
In Molina's absence, catching duties will be handed to Tony Cruz and Rob Johnson, both of whom are already on the roster. The Cardinals will also have a bench spot to fill, and because a DL move will be made, the team can recall outfielder/first baseman Brock Peterson even though he was just sent down over the weekend.
Molina sat out three games before the All-Star break after being diagnosed with inflammation. An MRI performed at the time revealed no structural damage in a knee that has previously been surgically repaired.
Molina caught the first 10 games out of the break before resting during Game 1 on Tuesday. He had not complained of any further issues recently, but the Cards have kept three catchers on the roster since the initial setback so that they would be protected in case the discomfort resurfaced.
Manager Mike Matheny could tell during Molina's two at-bats on Tuesday that his catcher was dealing with discomfort.
"Some days I was feeling better," Molina said, "but catcher is a tough position. You have to be 100 percent. You can't be 75 percent. Some days you feel good, but going up and down with me isn't helping."
Losing Molina for any substantial period of time could be costly to the Cardinals, whose pitching staff has thrived under his guidance and whose offense is keyed by his middle-of-the-order bat. Molina entered the day ranked second in the National League with a .331 batting average and third with 30 doubles. No catcher in the Majors has caught more innings than Molina this year, and he has a catcher's ERA of 3.27.
Molina had started 93 of the team's first 105 games.
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.