The St. Louis Cardinals have placed right-hander Adam Wainwright and catcher Andrew Knizner on the injured list, it was announced Wednesday.

Wainwright, 41, has been dealing with a right shoulder strain and left Tuesday's 15-2 loss to the Miami Marlins in the fourth inning -- his third consecutive outing of less than four innings.

During Wainwright's difficult three-game stretch, he has allowed 20 runs and 24 hits. The Cardinals have been outscored 29-2 in his past two starts. The veteran, who is 3-4 with a 7.66 ERA, has said he would retire after the season -- his 18th with the organization.

"There's not a whole lot behind him at the moment," manager Oliver Marmol said Tuesday. "This is a guy who's meant a lot to this organization. We're going to take a deeper look at this and he's determined to finish well."

Knizner suffered a right groin injury after being hit by a foul ball and was removed from Tuesday's game after the fourth inning. He was taken to the emergency room as a precaution before being released Tuesday evening.

The catcher is hitting .227 with five home runs and 15 RBIs over 15 games this season.

In related moves, the Cardinals called up catcher Ivan Herrera, right-handed pitcher Dakota Hudson and lefty Zack Thompson from Triple-A Memphis. Pitcher James Naile was optioned to Memphis.

The Associated Press contributed to this report.