MILWAUKEE -- Veteran right-hander Adam Wainwright will return from the 10-day disabled list and start the home opener for the Cardinals against the D-backs on Thursday. Rookie right-hander Jack Flaherty was optioned to Triple-A Memphis to make room on the roster for Wainwright.
"It means a lot to me," Wainwright said before Wednesday's game at Miller Park. "I had already in my mind gotten myself ready to pitch either tomorrow or whenever, I was just going to be ready."
To ensure that he was ready to return from a left hamstring strain, Wainwright was put through a myriad of drills and tests.
"I think they invented tests for me to try to pass to prove to them I was ready," he said. "I didn't do anything out of the ordinary to try to prove that I was ready. I went to them and I said, 'I'm ready to play, you can put me through every test you want to put me through.' But I did no lobbying."
Wainwright had said he didn't think the injury was serious enough to warrant time on the DL, but manager Mike Matheny said it was a medical decision.
"It was completely out of our hands," Matheny said. "When he has an MRI that shows there's something going on with that hamstring, he no longer has a say. He can't outwill an MRI."
Wainwright understood the early-season precaution but added, "If it had been in the playoffs, I would not have even mentioned anything and I would have gone out and pitched fine."
Flaherty, St. Louis' No. 2 prospect per MLB Pipeline, struck out nine and allowed one run over five innings against the Brewers in Milwaukee on Tuesday. In 25 starts between Double-A Springfield and Triple-A Memphis last season, he posted a 2.18 ERA and a 1.04 WHIP.

Wainwright's activation pushes the rest of the Cardinals' starters back one day. Right-hander Michael Wacha had been scheduled to pitch Thursday, but after Friday's off-day, he will now start Saturday against Arizona, followed by Luke Weaver on Sunday. Miles Mikolas will start on Monday at home in the series opener against the Brewers.
Wainwright, 36, is a three-time All-Star over 12 seasons for the Cardinals. Since missing most of the 2015 season due to an Achilles injury, Wainwright has posted a 4.81 ERA over 57 appearances (56 starts) for St. Louis from 2016-17.
Wainwright said he didn't think he'd be set back by the time off.
"I feel very good," he said. "I got my pitch count up to 90 for that last couple days of Spring Training, so arm strength-wise I'm where I need to be. Now, I've just got to go out and make pitches."