Glaus will begin physical therapy next week following Wednesday's surgery in Los Angeles. The 32-year-old hit .270 with 27 homers and 99 RBIs last season, his first with the Cardinals.
The recovery timeline would mean that the 2002 World Series MVP would miss the Cardinals' opener on April 6.
Glaus appeared at the team's annual Winter Warmup event last weekend and made no mention of an injury or a need for surgery. General manager John Mozeliak said the team first learned from Glaus over the Christmas holidays that he was experiencing some discomfort as he began increasing workouts in anticipation of the season. Glaus was sent to a team doctor in Florida.
An injection didn't help, and the team learned Monday that surgery was planned.
"It's a loss, but it's part of the game," Mozeliak said. "We'll be fine. We'll find a way to survive."
Mozeliak said the exact recovery time is uncertain and it was possible Glaus could be ready for Opening Day.
"I think there's a chance. It's really hard to guess when he'll return until he can start doing some baseball activities," Mozeliak said.
Glaus had two cortisone shots and missed a few games in September due to what was described as a strained right shoulder. But an MRI at the time showed no significant problems.
St. Louis has two highly regarded prospects at third base in David Freese and Brett Wallace, the team's 2008 first-round draft pick from Arizona State. Mozeliak said Freese is the front-runner to fill in until Glaus returns.
"Given where he played last year and the success he had at Triple-A, I would say that would be the natural progression," Mozeliak said.
The 25-year-old Freese is a St. Louis native who came to the Cardinals from San Diego in the Jim Edmonds trade in December 2007. He hit .306 with 26 home runs and 91 RBIs at Triple-A Memphis.
Wallace, 22, hit a combined .337 with eight homers and 36 RBIs in Class A and Double-A after signing with St. Louis.
Glaus finished in the top 10 among NL third basemen in RBIs, doubles, home runs and slugging percentage last year. He set a Cardinals team record for fielding percentage (.982) by a third baseman, a mark that led the league.
Glaus has a career batting average of .258, with 304 homers and 877 RBIs in 10-plus seasons with Anaheim, Arizona, Toronto and St. Louis. He is entering the final year of a contract that will pay him $11.25 million this year.