"I would guess Thursday if I was guessing," Duncan said with a smile after Isringhausen's throw.
Isringhausen has been sidelined since April 26 with a muscle strain on the right side of his ribcage, but the injury turned out to be less severe than the team originally feared. He threw off a mound on Friday, Sunday and again on Tuesday. For the last throw, Duncan stood at the plate in the home bullpen at Busch Stadium.
All of the sessions went well, and Isringhausen said he's plenty ready to return -- and to restore order to a bullpen situation that has been a bit chaotic in his absence.
I've been throwing better down there than I was probably when I got hurt," Isringhausen said. "It's all about my mindset. Things are going good. The ball is coming out of my hand good. I have good action on my pitches."
The St. Louis relief corps didn't exactly fall to pieces in Isringhausen's absence, as Julian Tavarez and Ray King present a solid left-right combination in the late innings with or without Isringhausen in the ninth. Protecting a lead wasn't often a problem, but the Cardinals did have some trouble keeping small deficits from turning into large ones.
With Isringhausen, the pen's best pitcher, back in action, the equation will change a bit.
Molina close? The only remaining question regarding Isringhausen is who will be sent out when he is activated. If Yadier Molina continues to improve rapidly, that question will have a fairly easy answer.
Molina, who suffered a sprained ankle on Sunday, took batting practice on Tuesday and has shown marked improvement in his condition two days in a row. If he's ready to play on Thursday, then the Cardinals would probably send catcher Mike Mahoney to the Minor Leagues to make room for Isringhausen.
As with Isringhausen, Molina's quick recovery has been a bit of a surprise. Manager Tony La Russa said that his starting catcher could well be in the lineup Thursday afternoon, before the Cardinals hit the road for a 10-day trip.
"That's what (head athletic trainer Barry Weinberg) told me," La Russa said.
"That would be really a heck of a lot different than what I thought on Sunday afternoon."
Today in Busch history: On May 10, 2001, Rick Ankiel made his last regular-season appearance as a Major League pitcher until returning in September 2004. Ankiel allowed three runs on three hits with five walks and two wild pitches in a game the Cardinals came back to win over the Pirates, 11-5. Jim Edmonds and Albert Pujols went deep for St. Louis. Thanks to Project Retrosheet (www.retrosheet.org) for the information.
Baby 'Birds: Jeremy Cummings pitched five shutout innings for Triple-A Memphis in a 3-2 win over Iowa on Monday. John Gall doubled twice and drove in two runs. ... Kevin Estrada homered and Reid Gorecki drove in two runs as Double-A Springfield came from behind to beat San Antonio, 7-5. ... Stuart Pomeranz pitched eight shutout frames, but Class A Palm Beach lost, 2-1, to Fort Myers in 11 innings. ... Matt Lemanczyk and Jarrett Hoffpauir each had three hits, including a double, for Class A Quad Cities in a 10-5 win over Clinton.
Pomeranz stands tall as the player of the day despite receiving no decision. He allowed eight hits but no walks and struck out eight to lower his ERA to 3.13. The 6-foot-7 right-hander was the Cardinals' second-round draft pick in 2003.
Coming up: Jeff Suppan goes for win No. 3 on Wednesday at 7:10 p.m. CT, facing off against the always tough Brad Penny. The series wraps up on Thursday afternoon with Chris Carpenter facing Derek Lowe.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.