Team spokesman Brian Bartow said Wednesday night that results of MRIs and other tests were being examined by Dr. Lewis Yocum in Los Angeles. The team anticipated a news conference Thursday afternoon to disclose the findings.
Wainwright, a 20-game winner and runner-up for the NL Cy Young Award last year, was sent back to St. Louis on Wednesday for tests and consultation with team physician George Paletta. Earlier in the day, general manager John Mozeliak said "things do not look encouraging" for the right-hander, who injured his elbow while throwing batting practice Monday.
Mozeliak stopped short of saying Wainwright would need season-ending Tommy John surgery.
"I don't want to speculate, but obviously ligament damage, that's usually what it results in," he said.
Bartow said Mozeliak remained pessimistic after the decision to seek a second opinion.
The 29-year-old Wainwright began feeling soreness Monday. Trainers examined him Tuesday and Wainwright flew back to St. Louis to meet with team doctors on Wednesday.
"It appears to not be good," manager Tony La Russa said. "We'll see, though."
The news comes one day after the Cardinals learned utility infielder Nick Punto will miss eight to 12 weeks because of a sports hernia that will require surgery.
Wainwright's injury is much more significant. Losing him would leave a big hole in what looked to be a stable starting rotation heading into camp. Chris Carpenter, Kyle Lohse, Jaime Garcia and Jake Westbrook have all had arm surgery during their careers.
There are few pitchers available on the free-agent market, with Kevin Millwood probably the best known.
"It's going to be tough to replace a guy who wins 20 games, but you never know," first baseman Albert Pujols said. "One of these young kids could step up like Jaime did last year."
The 6-foot-7 Wainwright went 20-11 with a 2.42 ERA last season, finishing behind Philadelphia's Roy Halladay in Cy Young balloting while making his first All-Star team. His 2.93 ERA since 2007 trails only Halladay, and no NL pitcher threw more than Wainwright's 463 1/3 innings during the past two seasons.
La Russa said he doesn't believe the injury is related to the soreness Wainwright felt toward the end of last season, when he didn't pitch in September. He said it's more likely related to minor issues Wainwright had in 1998 and 2004.
"It was so strange because he had a great throw his first time out," La Russa said.
In 2009, Wainwright led the NL in wins (19), innings (233) and starts (34), winning a Gold Glove while finishing third in Cy Young voting.
"You can't replace Adam," McClellan said. "Everybody is going to have to step up a little bit more. But we can't sit here and feel sorry about ourselves. I know everybody else we play isn't going to feel sorry for us."
La Russa doesn't expect the Cardinals to try to fill any void left by Wainwright through a trade or free agent signing.
"The answer is here," he said.
Punto was injured Saturday. A career .247 hitter, he batted .238 in 88 appearances last season with Minnesota. He hit a career-high .290 and scored 73 runs in 2006 with the Twins.
NL rivals expressed sadness as they learned of Wainwright's injury.
"Think the world of him, and arguably the last couple of years as good as there is in the league," Cubs general manager Jim Hendry said in Mesa, Ariz. "We've been on the other side of that, it's no fun. Competition-wise, you never want to see your opponents take a lesser step because of a serious injury, so hopefully he'll get better down the road and come back and be terrific."
Wainwright is 6-1 with a 2.61 ERA the past three seasons against Chicago and has won all five starts at Wrigley since the start of the 2008 season.
"That's a shame," Cubs manager Mike Quade said. "You want to win and compete and all the rest of it, but you don't like seeing anybody get hurt, that's for darn sure. I feel bad for him."
So did Cincinnati Reds manager Dusty Baker.
"I hate to see that," Baker said in Goodyear, Ariz. "Not only is he a good pitcher, but he seems like a fine young man. Every time I've seen him he was polite and respectful."