Isringhausen received a cortisone shot in his injured left hip on Monday, and he'll remain unavailable until at least Friday. Beyond that, though, it remains an open question.
"I don't know what's going to happen," he said on Monday afternoon. "I have no idea. We'll just have to find out Friday."
That's the day that Isringhausen will likely try throwing a bullpen session or a simulated inning to try out his hip. If it feels significantly better, he'll try to return to pitching. If not, a new set of questions will come into play.
"We'll find out more Friday," Isringhausen said. "I think maybe if I can throw off a mound on Friday, we'll go from there."
Updates: Jim Edmonds and David Eckstein both upped their activity levels on Monday, but only Eckstein did so with a real sense of optimism.
Eckstein, attempting to come back from a strained left oblique muscle, reported significant progress. He took ground balls and made throws for about 15 minutes and later was scheduled to take batting practice against a pitching machine.
"We're very encouraged by what's gone on here lately," he said.
Before Monday, Eckstein had been swinging hard, but only in soft toss and off a tee. Monday marked his first time swinging at a moving baseball since the injury. Eckstein said that he hopes to accompany the team on its upcoming road trip to Milwaukee and Houston.
Edmonds took batting practice and underwent a relatively typical pregame warmup after resting for a week.
"I did all right," Edmonds said. "I felt a little funky when I was hitting, but it cleared up a lot. I came through a lot quicker -- stuff just cleared up a lot quicker than normal, so I'm kind of excited about that."
Still, the outfielder said that the symptoms of his post-concussion syndrome are not gone yet.
"[I've had] a few less headaches, which is good news," he said. "Part of the anxiety is that I don't really know what the future holds. Hopefully, everything will get better."
Reyes will return: Right-hander Anthony Reyes will miss only one turn in the rotation as he deals with a "tired arm." Reyes was scratched from his scheduled Wednesday start, with Jason Marquis moving up from Friday to pitch on three days' rest. Reyes will return to the rotation next week against the Brewers at Miller Park.
"He's definitely on for the Milwaukee series," La Russa said. "It was just a day to take advantage of the off-day and give him a little refresher."
Late changes: When the Cardinals clubhouse opened to reporters on Monday, an unofficial lineup card hung where the normal card usually appears. It read, "For Pettitte" and featured the team's usual setup against left-handers -- including Preston Wilson as the leadoff man.
It was a tentative card, however, because La Russa knew that Astros starter Andy Pettitte wasn't a sure thing. By around 5 p.m. CT, Houston had announced that Pettitte would be pushed back, after all. In what may have been a bit of gamesmanship in response to the late announcement, the Cardinals didn't announce their revised lineup until approximately 15 minutes before game time.
The most notable change was the removal of Wilson from the lineup, with Chris Duncan inserted in right field at the No. 2 spot. Aaron Miles moved up from seventh to leadoff, Scott Spiezio moved from second to fifth, Juan Encarnacion from fifth to sixth and Ronnie Belliard from sixth to seventh.
Bits and pieces: Cardinals Care will present checks to area organizations on Tuesday that will bring the organization's all-time total to more than $10 million donated. ... Silver Slugger ballots have been handed out to coaches and managers. Albert Pujols and Scott Rolen are the Cards' best bets to win the awards this year. ... Adam Wainwright rejoined the team on Monday after leaving Arizona to be with his wife, who gave birth to the couple's first child.
This date in Cardinals history: On Sept. 11, 1964, the Cardinals made general manager Bing Devine look like a genius. Lou Brock, acquired from the Cubs three months earlier, went 3-for-5 with two RBIs as St. Louis beat Chicago, 5-0, at Wrigley Field. The losing pitcher? None other than Ernie Broglio, sent to the Cubbies in the same deal. Bob Gibson pitched a two-hitter, striking out six, for the win.
Coming up: Jeff Weaver will look to even his National League record to 4-4 when he takes the mound on Tuesday night against Pettitte (13-13, 4.34 ERA) at 7:10 CT.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.