ST. LOUIS -- Describing his 106-pitch bullpen session on Friday as "definitely my best by far" since resuming a throwing program in May, Chris Carpenter is on track to face hitters in a simulated game at Busch Stadium on Wednesday. That would represent a tangible step forward in his progression and put him on track to begin his Minor League rehab assignment in about two weeks, barring any setback.
Carpenter wanted to test both his stamina and the crispness of his pitches in Friday's side session, which was the most extensive he's had throughout his rehab program. Afterward, Carpenter was encouraged by how strong he felt throughout the four simulated innings.
"It's been a constant battle of consistency over the last few weeks," Carpenter said, "but today was a good throw and something that we can definitely build on."
"He threw very well and was very sharp," added manager Mike Matheny, who was among those to watch Carpenter throw. "He seemed to throw just as good in the [final inning] as he did in the first. You could see the stamina is there and that he's in terrific shape."
General manager John Mozeliak said that after Carpenter throws a simulated game next week, he will head to Florida to throw a second simulated game. That would likely take place the following Monday during the Major League All-Star break. If all continues to go well, that would have Carpenter in line to then begin a Minor League rehab stint later that week.
The Cardinals still intend to build Carpenter up as a starter in case the club wants to use him as such. That would require using most or all of the 30-day maximum period for a rehab assignment.
"I imagine we're going to use a lot of it," Mozeliak said. "But it could depend upon what's going on here [with the Major League club] and how he's throwing."
Carpenter has not set a timetable for his return -- "It's still one throw at a time right now," he said -- but recent progress has him again optimistic that he will pitch in 2013. Of that intention, he said: "I think I've got a pretty good shot."
Not only will he continue to monitor his improving arm strength, but Carpenter is also moving through this process aware that he has a back issue to maintain. Carpenter had to briefly shut down last month due to recurring back pain that stems from an injury he first suffered while lifting weights in January. This is an issue separate of thoracic outlet syndrome, which halted Carpenter's throwing program in February.
Carpenter has been told that he is not dealing with a herniated disc, but rather that there is ligament damage around a disc. Too much strain could risk further damage.
"It's something that we have to make sure we continue to keep sound, because that's what's leading to a lot of the issues that are going on," Carpenter said. "We are really concentrating to make sure the stability and strength around my low back has been good. And any sign that it starts getting out of whack, we back off and make sure we control it before I do something where it does turn into something severe."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. Chad Thornburg is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.