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8/27/2014 5:40 P.M. ET

Molina may be back behind the plate on Friday

PITTSBURGH -- Having gone through a Tuesday workout without any complications, Yadier Molina is scheduled to catch five innings as he begins a rehab assignment with Double-A Springfield on Wednesday. He could then be back in the Cardinals' lineup as early as Friday, when they open a home series against the Cubs.

Manager Mike Matheny acknowledged a Friday return as "a possibility," though that will obviously be contingent upon how the next two days go for Molina. Assuming all goes well on Wednesday, the veteran will be back behind the plate for Springfield on Thursday.

These will mark Molina's first game appearances since he left a July 9 contest against the Pirates after tearing a ligament in his right thumb on a slide into third base. At the time, the Cards expected to be without Molina for eight to 12 weeks. Friday will be his seventh week since undergoing surgery.

If Molina does return before rosters expand on Monday, St. Louis will have to make a corresponding roster move to clear space for him. The club is content with keeping three catchers on the roster, and it would likely make the subtraction from the bullpen, which has featured eight relievers since Monday.

Wacha throws first live BP to batters in Springfield

PITTSBURGH -- With general manager John Mozeliak among those in attendance to assess, rehabbing right-hander Michael Wacha threw three "innings" of live batting practice to a pair of Double-A hitters at Hammons Field in Springfield, Mo., on Wednesday.

The structured session was designed to allow Wacha to get a feel for how hitters were seeing his pitches. Though Wacha begun throwing off the mound 11 days prior, this was the first time since his June 17 start against the Mets that he had thrown with a hitter standing in the batter's box.

Wacha faced Patrick Wisdom and Charlie Tilson while throwing three sessions of about 15 pitches. He took a break in between each to simulate innings. A Cardinals front office member reported afterward that Wacha "looked good."

Wacha told reporters in Springfield that he expects to make a rehab start for Springfield in Tulsa on Sunday, which would put him closer to a return to the Cardinals' rotation. St. Louis has not confirmed that assignment, and the club will likely wait to do so until it sees how Wacha's arm responds from this test. Wacha has been sidelined since mid June with a stress reaction in his shoulder, an unusual injury for a pitcher and therefore one that the Cardinals have monitored with added caution.

Matheny: Cards want to 'push the envelope' on bases

PITTSBURGH -- As they do before the start of each new series, the Cardinals' coaching staff gathered all of the club's hitters in a room on Monday afternoon to prepare for what was on tap, but also to dissect what was still fresh. To that latter point, St. Louis used this most recent meeting to revisit the topic of aggressive baserunning after a sloppy series in Philadelphia.

The reminder has provided payoff, as both of the Cards' seventh-inning rallies against the Pirates have been aided by an aggressiveness on the bases. In Monday's one-run win, it was Matt Carpenter's move from first to third that led to a bobble by outfielder Andrew McCutchen and the opportunity for Jon Jay to take the extra base. Both then scored on Matt Holliday's go-ahead single.

On Tuesday, Jhonny Peralta's ability to scamper from first to third positioned him to score the tying run. Oscar Taveras, though he would be stranded on base at the end of the inning, also showcased some aggressive running.

"Push the envelope," Cardinals manager Mike Matheny said. "It's not running into outs, but in certain spots ... be aggressive. It all comes out of that first step. It's thinking the game. I think that's the mental training that is our job as a staff to keep challenging these guys about.

"I thought we did a real nice job last year in improving, and I think we've done a nice job this year as well. I think that's why we make such a big deal of it when it doesn't happen. If you're taking a great secondary lead and don't want to be a station-to-station baserunner, that's a mentality that we've tried to change."

Matheny added that he thought Peralta had taken it personally on Sunday when he did not advance to third on a flyout in the second inning. At the time, the Cards trailed the Phillies by only a run. St. Louis did not end up scoring in that inning.

"That aggressiveness that we didn't see in Philly, we're watching these guys do now," Matheny said. "We're going to keep doing that, keep the throttle down and be aggressive on the basepaths."

Worth noting

• The Cardinals still plan to start Justin Masterson on Saturday, but Matheny has not announced whether Masterson will pitch the first or second game of a doubleheader against the Cubs. St. Louis has not revealed who will start the other game.

• Triple-A Memphis increased its division lead to two games with a 9-6 win over Fresno on Tuesday. Six games remain in the season for Memphis, which hasn't had this large a lead all season. Xavier Scruggs, Audry Perez and Luis Mateo each contributed two-hit, two-RBI games in the most recent win.

• Randal Grichuk made his first start since being recalled as Matheny batted him second against Pirates lefty Jeff Locke on Wednesday. Grichuk, who hit .325 against left-handed pitching in the Minors, doubled off Locke in his first at-bat, one night after getting a pinch-hit RBI single off lefty reliever Tony Watson.

• After Wednesday's game, Matheny said the club still has "nothing concrete" as to the severity of the injury or how long Shane Robinson may be sidelined with a left shoulder injury. Robinson, who injured his shoulder sliding into second base in Monday's game, had returned to St. Louis on Tuesday to have his shoulder examined by team physicians.

• The Cardinals, through a partnership with Papa John's, will sell a limited number of $7 pavilion and terrace level seats to the club's Friday home games against the Rockies (Sept. 12) and Reds (Sept. 19) next month. Those tickets will be available for purchase at 10 a.m. CT on Thursday at cardinals.com/papajohns. There is a limit of six tickets per customer.

Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.