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8/9/2013 12:17 A.M. ET

Johnson's pitching appearance a first for Matheny

ST. LOUIS -- Rob Johnson's brief pitching appearance on Wednesday marked the first time in Mike Matheny's managerial tenure that he has asked a position player to take the mound.

Johnson, who has now made two relief appearances in his big league career, began preparing for the possibility of pitching in the fifth inning. He threw in the batting cage to get loose and later warmed up in the bullpen as Keith Butler labored through a 45-pitch ninth inning.

With Butler unable to secure the third out of the frame, Matheny called upon his backup catcher to face Dodgers reliever Paco Rodriguez

"We have a lot of pitchers that petition to be position players, and every once in a while, you get a position player that lets it be known he's not afraid to go to the mound," Matheny said. "Rob has done it in the past, so we knew that he would be ready to go."

Other than a few innings during his junior college days, Johnson's pitching background is limited. He threw a bullpen session while with San Diego in 2011 just to see what came of it. He ended up hitting 92 mph on the radar gun.

In 2012, Johnson pitched a scoreless inning in the Mets' 14-5 loss at Toronto. On Wednesday he started Rodriguez with two changeups, then secured the strikeout with two fastballs. His third pitch of the at-bat registered 90 mph on the stadium radar gun.

Asked if he looked up to see that figure, Johnson answered, "Absolutely."

"Previous to last year's outing, I had gotten on the mound a couple of times," he added. "This year I hadn't gotten on the mound at all. It was a little funky. I felt like I was using all arm. I was just trying to throw strikes."

By having Johnson close out the ninth, Matheny was able to avoid using a fourth member of the bullpen to cover for Shelby Miller's early exit. As a result the Cardinals entered Thursday's game with a relatively fresh bullpen.

Miller expected to be back on mound next week

ST. LOUIS -- On Thursday, one day after being stung on the right elbow by a line drive, Shelby Miller tested his pitching arm by playing catch. Encouraged by how well his arm responded to the exercise, Miller hopes to be back on the mound by next week.

Manager Mike Matheny substantiated that optimism by noting that a stint on the disabled list has "not been a part of the conversation."

"[It's] just a little sore, but nothing bad," Miller said. "I figured it would be a little worse than it was based on how that ball hit me. It feels really good. It feels loose. We're doing a little more treatment. I'm trying to see if I can pitch as soon as possible."

Although Miller expressed an interest in pitching as early as this weekend, that is not in the Cardinals' plans. Miller's next scheduled start was to be on Tuesday, though adjustments to the rotation now have Adam Wainwright in line to pitch that day. Miller would start at some point after that.

Miller still bears the seam mark on his elbow at the spot where Carl Crawford's line drive hit him squarely between two bones. Otherwise there is no evident day-after bruising.

"My arm is [sorer] after I pitch than it is now," he said. "To stay out there for 100 pitches last night, my arm would probably feel worse than it does right now. That's something to be happy about. I got lucky there."

Cardinals make adjustment to pitching plans

ST. LOUIS -- With their rotation already altered by Shelby Miller's abbreviated start on Wednesday, the Cardinals have decided to further tweak their pitching plans.

In addition to calling up Carlos Martinez to start on Thursday, the Cardinals now plan to summon right-hander Michael Wacha to pitch against the Cubs on Saturday. As a result, Joe Kelly will start on Sunday, and Adam Wainwright's next start has been pushed back, from Saturday to Tuesday. That not only gives Wainwright three additional days off, it lines him up to start the opener of next week's critical three-game series against Pittsburgh.

Lance Lynn remains Friday's scheduled starter.

"We talk about this long stretch of games and how our starters just continue to go out there on normal rest," manager Mike Matheny said. "We have an off-day coming. I think that's an opportunity to get Michael in there and give our guys a little more rest. And I think with what we saw with Jake [Westbrook] last night and a guy going [on] short [rest], I think it gives him an opportunity to get a little more rest on the backside as well."

The insertion of Wacha this weekend also provides the Cardinals with the flexibility to go in a handful of directions with the rotation against the Pirates. Miller hopes to be back that week, and Lynn would be fresh enough to pitch in either of the final two games of the series as well. That would allow the Cardinals the option of pushing Westbrook out of that series entirely.

That is an interesting proposition given Westbrook's career numbers -- 1-8 with a 4.98 ERA in 15 career games (11 starts) -- against the Pirates.

The Cardinals will have to add Wacha to the 25-man roster before Saturday, though that can be done by sending Martinez back down after his Thursday start. The Cardinals have not yet committed to how long Wacha's stay may be.

Wacha made three appearances for the Cardinals earlier this summer and allowed nine earned runs on 17 hits in 17 2/3 innings. Six of those runs and 10 of the hits were given up in one 4 2/3-inning start.

The organization put Wacha on a six-day rotation schedule when he returned to Triple-A in order to monitor his workload. In six starts since being demoted, he posted a 3.51 ERA, struck out 39 and walked four in 33 1/3 innings.

"We've been talking about Michael for a while, trying to get him back into the mix here," Matheny said. "It's been that balance all season, not getting the young guys too much, but also getting them enough. I think this will be a good opportunity to get Michael here."

Wacha and Martinez are currently ranked by MLB.com as the organization's top two pitching prospects.

Freeman excited to be back with Redbirds

ST. LOUIS -- Sam Freeman's arrival from Triple-A on Thursday provided the bullpen with a fresh reliever and someone who could be able to offer a multiple-inning appearance, if needed. He takes a bullpen spot from Keith Butler, who was sent back to Memphis after throwing 45 pitches on Wednesday.

Freeman, who had two stints with the Cardinals last season, posted a 2.95 ERA in 44 games with Memphis this year. He made 20 scoreless appearances from May 28 to July 26 and accrued 61 strikeouts in 64 innings. He has also learned to manage the impingement in his left shoulder that ended his 2012 Arizona Fall League stay early and then interrupted his Spring Training.

"I'm excited. I'm ready to go out and get outs," Freeman said after flying from Reno to St. Louis on Thursday. "I'm just trying to strip it down to the simplest form and get outs."

The Cardinals also sent first baseman/outfielder Brock Peterson to Memphis on Thursday. That move was necessary in order to clear roster room for Thursday starter Carlos Martinez. The Cardinals are consequently left with a four-man bench, and it will likely remain that way at least through Saturday, since they have plans to call up right-hander Michael Wacha for a start.

Worth noting

• Concerned that his comments from Wednesday night had been misinterpreted, manager Mike Matheny clarified on Thursday that his explanation about how the next-day starter is prepared to pitch in an emergency was not meant to be a blanket statement. Circumstances and who that next-day starter is, Matheny said, play a role in determining whether to use that starter or turn the game over to the bullpen.

"There's no policy. There's no rule," Matheny said. "We stay pretty fluid, and we stay in contact with our guys, and they see if we have some young pitchers who we keep firing out there who have never done this before. Yesterday we were in a bind. And Jake [Westbrook] knew. Now, do we have it written in their contract that they have to be ready? There's nothing formal about it. If that's how it came across, then that's an apology I need to give, because that's not the message. That's not the truth. The truth is that our guys realize that sometimes we have to adjust to do what we need to do."

Not wanting to use relievers Kevin Siegrist and Seth Maness because of their recent workload, Matheny felt his best option was to go to Westbrook.

"Yesterday was the perfect storm of things that we didn't want to happen," he said. "We were stuck in a spot, and Jake realized that and took care of us."

• According to Matheny, catcher Yadier Molina (sprained right knee) was scheduled to swing a bat on Thursday for the first time since landing on the disabled list. Molina is eligible to come off the 15-day DL next Thursday, though it is still not known if he will be ready by that date.

• Matheny chose to start catcher Rob Johnson instead of Tony Cruz on Thursday because of Johnson's rapport with rookie starter Carlos Martinez. Until his callup to St. Louis last month, Johnson was the primary catcher for Triple-A Memphis.

• The Cubs are scheduled to start the following pitchers in the upcoming series at Busch Stadium this weekend: Chris Rusin (1-1, 3.98 ERA), Carlos Villanueva (2-8, 4.26 ERA) and Edwin Jackson (7-12, 4.96 ERA).

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.