Eagles trainer Rick Burkholder said Andrews had the surgery in California on Tuesday and the recovery time could be as long as three months.
"We've had before guys come back in five weeks, guys have taken three months," Burkholder said Wednesday. "It depends on when he gets his strength back and his symptoms go away. So we're just going to play it week-by-week with him right now."
Andrews will begin rehab immediately and visit the surgeon, Dr. Robert Watkins Sr., again later in the week for an exam. A decision will be made then about when he can return to Philadelphia.
Burkholder said the injury was related to a herniated disk Andrews had in high school. He received an injection for it then but had not experienced any problems during college at Arkansas or after being drafted.
Andrews had not played since aggravating the injury in Week 2 against Dallas on an extra-point attempt. Burkholder said Andrews took on a double-team and immediately began feeling pain.
"We think that this was the best approach for Shawn and once he gets through the rehab process we can sail ahead with him," Burkholder said.
Max Jean-Gilles has filled in for Andrews the last four games. He has played well in Andrews' absence, coach Andy Reid said.
"He's improved every week," Reid said. "The guys around him have a lot of trust in him. He's playing good football right now."
Quarterback Donovan McNabb said the offense has full confidence in Jean-Gilles.
"You can tell that he's comfortable. And we know that he's a talented guy and a big body and a guy who can move."
Jean-Gilles practiced with the starters for much of training camp as Andrews sat out while battling depression. That has eased his transition to the starting lineup, McNabb said.
"We just wish the best for Shawn and make sure that he has a speedy recovery to come back and be ready to go," McNabb said.
While they will not have Andrews, the Eagles should see the return of several players for Sunday's game against Atlanta.
Running back Brian Westbrook, who sat out the Eagles' 40-26 win over San Francisco before the bye week with broken ribs, should be back along with Kevin Curtis, who has not played since having surgery in August to repair a sports hernia.
Copyright 2008 by The Associated Press