"He's been progressively getting better, but it's a tough time to try and continue to work on things," Matheny said of Wacha. "But we like him. We like him in any situation, and we explained to him that there is the potential that that could change over time. He's got to stay ready, be available in the 'pen, and if we're fortunate enough to move forward, things could be different.
"It's been a challenge for him with the injury that he had and the time that he took. He's made great adjustments, but right now we have to go with the guys who we believe are going to give us the best shot."
After missing 11 weeks while dealing with a right shoulder stress reaction, Wacha returned to make four September starts. There were enough lingering concerns after the first two that the Cardinals pulled back the reins and had Wacha rest for 10 days. He pitched better his final two times out and finally saw his changeup return, but Wacha still had not pitched beyond the fifth inning.
After learning on Wednesday what his NLDS role would be, Wacha said he had anticipated that the Cardinals would go in this direction.
"I was kind of expecting it," Wacha said. "I never made it back to where I wanted to be as a starter, but I'm excited they're going to take a chance on me in the bullpen. Hopefully, I make a pretty good impact in there."
The reason for the Cardinals' push to see if Wacha could be more than a reliever was obvious, as no one had forgotten what the 23-year-old meant to the club's postseason run a year ago. Wacha won his first four postseason starts in 2013, which included a pair of wins against the Dodgers in the NL Championship Series. Both times, Wacha outdueled Clayton Kershaw. For his 13 2/3 scoreless innings in that series, Wacha took home NLCS MVP honors.
How Wacha could be used against the Dodgers this October remains fluid. Matheny implied that he has no plans to disrupt the back end of the bullpen -- Seth Maness, Carlos Martinez, Pat Neshek and Trevor Rosenthal -- because of the role those relievers played in helping the Cardinals capture a second straight division title.
Wacha could be used in long relief, though the Cardinals also don't seem ready to pigeonhole him into that role.
"We aren't where we are right now if we haven't had the guys who are in our bullpen already doing what they've done," Matheny said. "To bail on that right now isn't the game plan. [Wacha] is going to be an extra weapon for us. We'll obviously see what we need."
A bullpen role won't be entirely foreign to Wacha, who pitched five times in relief for the Cardinals last season before working his way back into the rotation in September.
"I threw a little bit out of the bullpen last year and it didn't take me long to warm up," Wacha said. "I think the adrenaline will be pumping while I'm out there and the arm will feel pretty loose within a few throws. It's definitely a different game plan. As a starter, you have a little bit more time to develop all your pitches. As a bullpen guy, you have to come out there and have all your pitches ready to go for that batter. I'm looking to come out there any time I can and try to get some outs."