La Russa had tests Tuesday at the Mayo Clinic, whose physicians consulted with Cardinals doctors and decided it would be best for the manager to rest and allow his medication to take effect.
St. Louis started a series at Chicago on Tuesday night, with the road trip wrapping up Sunday at Cincinnati. It was uncertain whether La Russa would definitely rejoin the team next Monday for the start of its four-game home series against Philadelphia and Houston.
Bench coach Joe Pettini will run the Cardinals while La Russa is away. The 66-year-old La Russa is in his 16th season as St. Louis manager.
Pettini said La Russa's condition reached a point where something had to be done.
"He gutted it out for the games. But before the game every day you come in and ask 'How you doing skipper?' and you're hoping to get a little better answer. But every day he would shake his head and say, 'Not any better, not any better,'" Pettini said.
"So he's been in agony and we're very concerned and we're hoping with this physical out at the clinic in Arizona that it's going to figure out what needs to be done," Pettini said. "If he needs to take some time, take the time or whatever."
La Russa's problem was initially identified in mid-April as conjunctivitis, an inflammation commonly known as pink eye. But last week he called his illness a viral infection.
The entire right side of La Russa's face was swollen for a while, although La Russa continued to hit fungoes at practice until the last homestand.
Cardinals general manager John Mozeliak said La Russa had previously scheduled a physical at the clinic in Arizona.
"But obviously, since he's been diagnosed with shingles, he's also having that reviewed and meeting with a few different specialists just to see if there's any way to relieve his discomfort," Mozeliak said.
The illness appeared to improve cosmetically last week, but La Russa said it was still an effort to keep his right eye open.
"I'm not doing much," La Russa said before a game then. "I had to shut it down because I just can't hang in there. It's hard to hit one-eyed."
La Russa said managing games has been easier because of the adrenaline involved.
"You handle that better than you do before and after," he said. "The game is not that tough, it just doesn't bother you as much."
Cardinals shortstop Ryan Theriot said La Russa has been in obvious pain for a while.
"He's been struggling. People don't even realize. This has been a long ordeal for him," Theriot said. "And he's really battled through it and pushed through it. He's been a trouper, man. But he's got to get well. He's been hurting, he really has been."