ST. LOUIS -- After missing his start Friday night with back spasms, Adam Wainwright is set to start Sunday in the Cardinals’ series finale against the D-backs at Busch Stadium. The 1:15 p.m. CT matchup will be available free on MLB.TV.

Pushing Wainwright to Sunday also pushes Miles Mikolas back to Monday against the Pirates, then Jack Flaherty to Tuesday. Manager Mike Shildt said Daniel Ponce de Leon will start Wednesday, earning another opportunity after allowing one run in 6 2/3 innings Friday night in place of Wainwright.

It hasn’t been decided yet whether Michael Wacha will stay out of the rotation. He began to warm up in the bullpen during Saturday night's 4-2 win over the D-backs when Dakota Hudson loaded the bases with no outs in the second inning, but Hudson pitched out of the jam.

Wacha is 5-4 with a 5.54 ERA this year. He was moved to the bullpen in May to work on his velocity and command, but he returned the rotation in June and pitched inconsistently. In his last start -- July 4 against the Mariners -- he gave up four runs in 3 1/3 innings before Ponce de Leon relieved him.

Earlier in the season, Ponce de Leon was asked to shore up his pitching enough to be a starter for the Cardinals. With a 1.99 ERA in four starts and three relief outings, Ponce de Leon has filled a variety of roles and forced the Cardinals into deciding.

“He’s done it all,” Shildt said about Ponce de Leon.

Wainwright felt the back spasms Thursday night while he was getting out of bed, but he felt better Friday and said he could have pitched. The Cardinals didn’t want to push Wainwright and had Ponce de Leon as a viable alternative. The 37-year-old Wainwright has had back problems in the past and pitched through them, causing him to overcompensate. That eventually led him to the elbow problems he had in 2017 and '18.

“I’ve pitched with way worse back situations than [this],” Wainwright said. “But I told Shildt, ‘I want to pitch well.’ I feel like I’m on the verge of doing that for a really long time. I don’t want to have a setback.”

As the Cardinals figure out the rotation for the second half of the season, Wainwright expects to be in it, and the Cardinals expect him to be, too.

“He’s been efficient, he feels good. If he does that, he’ll stay healthy,” Shildt said. “We banked in some time, but this first stretch with however many games in a row, there’s going to be a turn where guys have to take that ball every fifth day. Then we can adjust after some off-days.”

Wainwright is 5-7 with a 4.31 ERA this year in 16 starts (87 2/3 innings). He’s brought some consistency to a Cardinals rotation searching for it and is on pace to throw more innings than he’s thrown since 2016, when he threw 198 2/3 innings.

He still wants to be the 200-innings pitcher he’s been in the past.

“That’s still my goal,” Wainwright said. “I want to push it the second half and have a little return to form. I’ve been really close to doing a lot of things like I want to do them. I want to continue to get better and make those strides.”