Chavez was moved from the 15- to 60-day disabled list Tuesday. He was placed on the DL May 1 with a strained right forearm, a move retroactive to April 25. He experienced back spasms May 10 and underwent an MRI exam one day later.
"We're at a pretty serious point," Athletics assistant general manager David Forst said before Tuesday night's game against Tampa Bay. "We're doing everything we can medically to get him back on the field."
Chavez, who was once among the game's brightest young stars, has played sporadically over the past few seasons due to various injuries. When he has played, he's often played hurt.
Now, Chavez, who is rehabbing in Arizona and was hoping to rejoin the team on its next homestand, is facing a tenuous playing future. According to the report, doctors have told him that the disk could go at any time. He learned it was herniated last week, when his back went out when he stood up from a chair.
"To say the least, I was really thrown by that information," Chavez said, according to the Chronicle. "It's disheartening. It was kind of the worst-case scenario. ... Hopefully, it's another 10 or 15 years, but I've just got to be careful now. It goes beyond baseball."
Between 1999 and 2006, Chavez hit .271 with 212 home runs, 241 doubles and 710 runs batted in and won six gold gloves at third base. But since 2007, he has played in just 121 games, batting .233 with 107 hits, 17 homers and 61 RBIs.
Chavez knew he would eventually need spinal fusion surgery, but he thought that was 10 to 15 years down the road, according to the report. But now it's known that his L3-L4 vertebra is significantly herniated, rather than a bulging disk. If it goes out, he will have to have it fused with the L4-L5 vertebra, which he previously had repaired. That procedure would rule out a return to the field.
"This last [diagnosis] is a little bit of a punch in the gut for everyone," team general manager Billy Beane said, according to the report. "Especially for Eric, because he's worked so hard and dealt with so many issues."
Chavez has one year left on a six-year, $66 million deal. When he found out about the recent diagnosis, he called Beane to convey his frustration and disappointment at not being able to contribute more, given the team's investment in him, the Chronicle reported.
"The whole length of the contract, it's been one thing after another. It's been a disaster, and I know what kind of predicament I've put Billy in," Chavez said, according to the report. "Now, with the back thing, it's like, 'You've got to be kidding me.' There's nothing that can be said that I haven't thought myself."
Chavez was placed on the DL with a strained right forearm earlier this month, retroactive to April 25 -- his fourth stint on the DL in the past three years. He played just 23 games last year before surgery to repair a torn labrum in his right shoulder.
Chavez is hopeful of returning this season, but it will be at least five weeks before that might happen.
"He's optimistic," Athletics manager Bob Geren said.
Also, injured infielder Nomar Garciaparra, out since April 29 with a strained right calf, could be activated from the 15-day disabled list Wednesday.
"It is getting better," Geren said. "He's close."
The Athletics made several other roster moves on Tuesday, including purchasing the contracts of right-handers Edgar Gonzalez and Chris Schroder from Triple-A Sacramento. Pitchers Sean Gallagher and Gio Gonzalez were optioned to Sacramento.
Edgar Gonzalez could take Gallagher's spot in the rotation and start Saturday's game against Arizona.
Minor league outfielder Javier Herrera was released to make room on the 40-man roster. Oakland plans to try and re-sign Herrera, who will likely undergo season-ending shoulder shortly, to a minor league deal.
Backup catcher Landon Powell, who hurt an hamstring running out a ninth-inning grounder Monday night, was sore but available off the bench.
Minor league catcher Curtis Thigpen, sidelined by a back injury, is set to join Oakland's extended spring training team, while Sacramento catcher Joel Galarraga went on the DL with a right shoulder strain.
Information from The Associated Press was used in this report.