In an interview with the Contra Costa Times, Cardinals manager Tony La Russa mentioned the possibility of putting McGwire on the team's active roster on Aug. 31 so he'd be eligible to play in the postseason, if the Cardinals are still in the race.
"If we're in contention, we'll put him on the roster Aug. 31. It's a nice little dream," La Russa told the newspaper.
However unlikely the scenario might be, La Russa said it's not impossible.
"Is it likely? Probably not. I don't think it's a zero possibility. The point is, you'll see him in spring training. He won't be leaning on the batting cage chatting it up. He'll work his [butt] off, and hitters will be thrilled he's there helping them," La Russa told the newspaper.
La Russa was speaking to the newspaper to promote his Animal Rescue Foundation's benefit event that will be held Saturday night in Northern California.
McGwire, who once again failed to be elected into the Hall of Fame due to performance-enhancing drug accusations, hasn't addressed the media yet about his new role with the Cardinals.
La Russa said McGwire could talk to the media by the end of January but definitely before spring training begins.
"He knows he's got to be forthcoming sooner than later," La Russa told the newspaper. "Now that we're past the holidays and awards, I think it'll happen soon. ... I'm curious to see what he says. I know enough about him and his character, I know he's a quality guy."
Eighth on the career list with 583 homers, McGwire has been stigmatized since evading questions from Congress in 2005 about performance-enhancing drug use.
McGwire received 128 votes (23.7 percent) in the 2010 Hall of Fame voting, 10 more than last year and matching the total from his first two times on the ballot.
"At least he didn't go backward," La Russa told the newspaper. "Hopefully now he'll get back [in voters' good graces] where he's out working again."
Jack O'Connell, secretary-treasurer of the Baseball Writers Association of America, told ESPN.com that if McGwire were to appear in a game in 2010, he would have to wait five years before going back on the Hall of Fame ballot.
But McGwire's candidacy would not start fresh: Since his name has already been on the ballot four times, McGwire's candidacy would resume with his fifth appearance. Players are eligible to be voted on a maximum of 15 years before their names drop off the BBWAA ballot.
O'Connell mentioned Minnie Minoso and Jose Rijo as players who appeared on the Hall of Fame ballot previously, then came out of retirement and had to wait five years to be eligible again.
La Russa is confident that McGwire will make a great hitting coach. McGwire has a lot of talent to work with, including reigning MVP Albert Pujols and Matt Holliday, who agreed to return this week to the team with a seven-year, $120 million contract.
"He's so enthused about this hitting thing," La Russa told the newspaper. "I know intimately what he teaches, and that's one reason I'm excited about him getting out and sharing it. It's very straightforward. ... I put my credibility with him. I believe it will work. He will not only be a great coach, but when he comes forward and whatever's said, we'll be able to go forward."
Information from ESPN.com's Jerry Crasnick and The Associated Press was used in this report.