PITTSBURGH • While catcher Yadier Molina sped toward his return to the majors with the first start of his rehab assignment, his partner in recovery, Michael Wacha, gained clarity on his own route back to the Cardinals.

Wacha threw three simulated innings and 45 pitches Wednesday afternoon in Springfield, Mo., and if he recovers from the outing today he’ll be scheduled to start Sunday for Class AA Springfield at Tulsa. The Cardinals confirmed the schedule after the righty disclosed it to reporters gathered at the affiliate’s Hammons Field for his live batting practice.

Molina is set to complete his rehab assignment before Wacha begins his.

Molina started at catcher and played six innings behind the plate for the Double-A Cardinals on Wednesday night. Molina had two hits in three at-bats, and he doubled home a run. Barring a setback, he’ll start again today for the S-Cards.

Manager Mike Matheny repeated Wednesday that his Gold Glove-winner might need “a couple days of catching” to prove healthy enough for a return, which could come as soon as this weekend. The Cardinals are open to the possibility that Molina will rejoin the team Friday when the club starts a four-game series against the Chicago Cubs at Busch Stadium. Molina will be seven weeks removed from surgery to repair a ligament in his right (throwing) thumb.

Matheny has described the decision on when to activate Molina as a medical decision more than a baseball decision. The catcher is using the games to prove his health and durability and whether he can comfortably throw and swing aggressively at game speed.

“He’s a great player,” pitcher Adam Wainwright said. “He’s one of the greatest catchers ever.”

With the exception of Saturday, when the doubleheader allows the Cardinals and Cubs to add a player to their rosters, the Cardinals cannot expand beyond 25 men until Monday. Matheny said the club would be open to carrying three catchers — with Molina joining backup Tony Cruz and July addition A.J. Pierzynski — during the weekend series. The Cardinals had an extra pitcher for the three-game visit to Pittsburgh.

PERALTA LOOKS TO PUSH

Overshadowed by the late-game rupture that led to Tuesday’s 5-2 loss at PNC Park was Jhonny Peralta’s savvy run from first to third base that led to the Cardinals momentarily tying the score at 2-2. Matheny said that the veteran shortstop “took it personally” when he didn’t tag up from second base and take third on a fly ball last weekend in Philadelphia.

By not taking the extra 90 feet, Peralta cost the Cardinals a run, just as he created a run for them a few days later by pushing for third base.

“Right there in (Philadelphia) in that situation, I know I can make it to third base,” Peralta said. “I didn’t know the center fielder. That’s my fault right there. I need to be better at that. I need to know the arm that he has.”

Matheny has recently urged all his players to be more aggressive on the bases.

“I’ve challenged each of the guys individually — what could you have done more aggressively?” the manager said. “I think you always have to err on the side of being aggressive to put the pressure on the defense. If you’re always trying to push the envelope you’re putting it on them to make a play.”

MILLER, MYERS LAUNCH APP

Cardinals starter Shelby Miller and reigning American League rookie of the year Wil Myers, of Tampa Bay, will launch a baseball game app today for mobile phones and tablets. The game, designed by Moonshark, is called “Wil & Shelby’s Baseball Battle.” It allows players to challenge friends to a baseball game that features both hitting (Myers) and pitching (Miller) contests. Users earn coins to outfit their stadium or improve their equipment. A “Shelby-approved” Redbirds-style jersey can also be purchased.

Miller joked that he’s not sure if his baseball app will replace “Clash of Clans” – a strategy game based on expanding and raiding villages – as the Cardinals’ clubhouse favorite.

Myers and Miller, who played against each other in the minors and sometimes golfed with each other, are represented by CAA, which helped stitch the two together for the app. There are a lot more places for players to increase their profile through new media than waiting around for the Wheaties box of yore or latest video game cover.

“Hopefully people will use it, play it, kill some time with it,” Miller said. “It’s definitely a step in that direction of getting our names out there a little bit more in the baseball world. It’s cool to be associated with a game.”

EXTRA BASES

• Matheny declined to announce who will start the second game of Saturday’s doubleheader against the Cubs, saying only that the “young pitcher” had not been told by the organization yet. Marco Gonzales, the 2013 first-rounder who made starts earlier this season for the Cardinals, is on schedule to start that day if invited, and he could be added as the allowed 26th man for the doubleheader. 

• Righty Justin Masterson expects to start the first game of the doubleheader, and he had what he and Matheny described as a bullpen session focusing on “simplifying” his mechanics after two difficult outings.

• Andrew McCutchen (rib) returned to the Pirates’ lineup and was able to play the entirety of Wednesday’s game despite the return of soreness in the area that put him on the disabled list this month. Pedro Alvarez did not return and had been diagnosed with a foot strain, and right fielder Travis Snider left Wednesday’s game with an injury.

Derrick Goold covers the Cardinals and Major League Baseball for The Post-Dispatch. Follow him on Twitter at @dgoold or on Facebook at Facebook.com/BirdLandPD

Derrick Goold is the lead Cardinals beat writer for the St. Louis Post-Dispatch and current president of the Baseball Writers' Association of America.