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7/6/2013 8:50 P.M. ET

Cards awaiting MRI results on Molina's knee

ST. LOUIS -- Catcher Yadier Molina left Busch Stadium late in Saturday's game to undergo an MRI exam in an effort to determine the cause of irritation in his right knee. The Cardinals will have the results of those tests by Sunday, but remain optimistic that they won't be without their standout catcher for long.

"He could be good enough to go tomorrow," manager Mike Matheny said after the team's 5-4 win over the Marlins. "We just want to rule things out and get a good look at it."

According to Matheny, Molina's knee began to bother him during the final innings of Friday's game. Molina was ruled unavailable to play on Saturday, though the club did not divulge that information until postgame. The knee that is bothering Molina now is the same one the catcher had operated on in Sept. 2007.

Molina, who has started 78 games as catcher, leads the National League with a .346 batting average. Tony Cruz started in Molina's place on Saturday and finished 1-for-4.

Cards shift rotation for two Wainwright starts

ST. LOUIS -- Cardinals manager Mike Matheny will again mix up the rotation next week, this time flipping Shelby Miller and Adam Wainwright's starts, so that Wainwright returns to the mound twice before the All-Star break, including next Sunday in Chicago.

Matheny said he discussed the change with Wainwright beforehand to gauge his preference in getting the additional start versus possibly missing out on the opportunity to pitch in the Midsummer Classic.

"He was adamant with the fact that he would love to have two starts and he knows what that does for our club," Matheny said. "Not undermining or demeaning the value of being on the All-Star team or starting the All-Star Game, he was very clear that he wants to do what he can around here to help us win."

When the decision to bump Wainwright up in the rotation was made, both Matheny and the ace right-hander assumed that it would take Wainwright out of consideration for pitching in the All-Star Game. But a recent rule in the Collective Bargaining Agreement states otherwise.

Wainwright, by rule, will still be permitted to throw a maximum one inning in the All-Star Game. He also will have the option of giving up his roster spot to another pitcher if he chooses not to play.

The Cardinals have not commented on whether they'll allow Wainwright the opportunity to pitch in the game at Citi Field on July 16. Alerted of the revised rule, Wainwright said he would like the opportunity to pitch. Wainwright will make this decision as well with the team's best interest in mind.

"The first thought is it's cool to pitch in the game, obviously," Wainwright said. "But I think what's more important is what's going on inside this clubhouse and can I help the team in that capacity. I think I can and I think our staff has trust in me to do that as well. Two more starts before the break gives us a good chance to win those games."

The Cardinals can then rework their rotation again after the break.

Adams' work paying off with sound defense

ST. LOUIS -- Count Matt Adams among the many he has surprised with his steady defense at first base.

Following up on a pair of impressive catches on Thursday against the Angels, Adams made another diving stop and tossed to pitcher Jake Westbrook for the out at first in Friday's 4-1 win over the Marlins.

Adams, who slimmed down in the offseason, credits third-base coach Jose Oquendo with helping him get into the best position before the ball comes off the bat, allowing Adams more time to react.

"Last year, I wouldn't get to the balls I got to the past two nights," Adams said. "Just the work that I put in in the offseason and the work that Jose's been doing with me since Spring Training."

While the Cardinals don't take infield practice before games, something Matheny said is essentially extinct at the big league level, the players make up for it with daily ground-ball work, which has helped Adams maintain his skills without consistent in-game fielding opportunities.

"Just keep taking ground balls because the days that I'm not in there, I've just got to stay fresh with that so the glove stays smooth and I'm ready for whenever the games pick up," Adams said.

With an eight-game stretch in American League ballparks, Matheny preferred to insert a starter into the designated hitter spot, giving them a half-day off, allowing Adams to slide into the lineup. On Friday, Carlos Beltran was given the night off, moving first baseman Allen Craig to right field, again opening up an opportunity for Adams.

"It was a great chance for us to watch him flop around on the field, have him diving all over the place, kind of see him on a consistent basis defensively," Matheny said. "When you have that designated hitter option, to me that's something that these veterans guys have earned, a little time off to be able to still keep their swings going."

Worth noting

• Carlos Martinez made his eighth start for Triple-A Memphis on Friday as the former reliever continues to be stretched out for spot in the rotation. Martinez allowed one run -- his first Triple-A home run -- and scattered six hits and four walks with one strikeout in 5 1/3 innings. The right-hander has allowed two runs or fewer in all eight of his starts.

• Pete Kozma was out of the lineup for a third straight game on Saturday as he continues to try and find his swing and build his confidence at the plate. Matheny said on Saturday that Kozma had a "great" batting practice on Friday and is moving in the right direction.

"We went in pretty much knowing this was going to be the case," Matheny said. "We'll see. There's nothing wrong with just kind of watching and seeing how things go."

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