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3/5/2014 7:09 P.M. ET

Efficient Miller impresses in first spring start

JUPITER, Fla. -- Aside from Adam Wainwright, who will start for St. Louis on Thursday, the Cardinals have now watched each of their starting pitchers take the mound in a spring game. And with his outing on Wednesday, Shelby Miller set the early bar.

After giving up a leadoff homer to Daniel Nava, Miller retired the final eight batters he faced. He struck out five, featured an improved curveball and showcased a developing cut fastball that Miller believes could be a new weapon. He did all this while being efficient (35 pitches in 2 2/3 innings), a quality that came and went during his rookie season.

"I know competing here is what it's all about," Miller said. "If I feel good, physically feel good and feel the ball coming out of my hand good, everything is going to be there eventually."

The competition he finds himself in this year is a bit different from the one he emerged from last year as the team's fifth starter. That was Miller's job to win. This year, the rotation spot is his to lose.

"Am I comfortable knowing that I have a better shot making the team? Yeah," Miller said. "But at the same time, nothing is guaranteed here, especially with all the young guys that we have. All of them have great arms. My job is to help this team win and pretty much pitch to keep my spot. Because you never know what is going to happen with these guys. They are so good and there is so much ability around here that I feel like I am still competing to keep my spot right now."

Miller has another four spring starts scheduled during which he can solidify that rotation spot. He's not waiting that long, though, to start leaving an impression.

"We talked about our [workout groups] and some of our young guys leading groups, Shelby absolutely took that personally and took pride in the fact that he could be a leader," manager Mike Matheny said. "The way he's going about his business, just the professionalism, he's made some real nice strides in that regard."

Matheny works through first replay challenge

JUPITER, Fla. -- After weeks of working through the mechanics of challenging a call through Major League Baseball's expanded instant replay, manager Mike Matheny had his first true trial run on Wednesday. What he learned is that there are still a few adjustments to be made with how he handles the procedure.

Upfront that he was going to be aggressive in finding a chance to challenge a call -- if only just for practice -- Matheny found an opportunity to go through the exercise in the eighth inning of an 8-6 victory over the Red Sox after outfielder Stephen Piscotty bounced a ball back to pitcher Noe Ramirez, who started an inning-ending double play.

Ramirez's throw to second base, however, forced Heiker Meneses to lunge for the catch as he tried to record the out. Matheny, thinking that Meneses' foot may have come off the bag in the process, headed toward second base to start buying time for the Cardinals' video replay staff to determine whether the call should be challenged.

Matheny slowed from a jog to a walk -- something he said he'll be more cognizant of in the future to give his video staff time -- and then positioned himself near second-base umpire Jon Byrne in a way where he could still see into the dugout. If all runs smoothly, bench coach Mike Aldrete will then give Matheny a signal as to whether or not he should challenge.

The difficulty on Wednesday, though, was that the teams were not dealing with the same technology that will be in place during the season. The television broadcast was on a slight delay, which did not allow the Cardinals' video coordinator time to immediately review the tape.

As a result, Matheny had to choose to challenge -- which he did -- before getting input from his staff.

"I could tell there was some deliberation and there was a delay [in the video room], and at the point where we were in the game, there was no reason not to," Matheny said. "And knowing that everybody was trying to get their hands around this anyhow, everything pointed in the direction of we needed to.

"Typically, if we have that window, we're going to have enough time. By the time he got it through the delay and got a look at it, it wasn't 10 or 15 seconds later that the people back here knew what we needed to do. I probably had more time to buy and then get what they had. But by the time I looked it all over, it was the right thing to do to use the challenge up."

Once the challenge was requested, crew chief Jerry Meals put on a headset to communicate with an additional umpire watching the replay from a truck. The out call was confirmed. The entire process, beginning with Matheny emerging from the dugout, took less than two minutes.

"It didn't seem to slow things down all that much," Red Sox manager John Farrell said. "I think what they discovered in the [Arizona] Fall League [practice runs] was about a minute and 15 [seconds]. But there's some in between innings that are up to four minutes, which is what's been trying to be cut down. But that wasn't an abnormal delay."

The Cardinals expect to have instant replay available four more times in Grapefruit League play. Before then, Matheny will remind his players and pitcher to remain in a holding pattern next time an inning-ending play is challenged. In this instance, the Red Sox defenders left the field, and the Cardinals' next reliever came onto it. Neither is supposed to happen.

"The whole thing was kind of a mess," Matheny said of that confusion. "There's going to be some lumps."

In Spring Training, managers are allowed an unlimited number of challenges in selected games to practice the procedure. During the regular season, managers will have at least one challenge to use. If any portion of a challenged play is overturned, then the manager who challenged the play will retain the ability to challenge one more play during the game. No manager may challenge more than two plays in a game. Once the manager has exhausted his ability to challenge plays during the game and after the beginning of the seventh inning, the crew chief may choose to invoke instant replay on any reviewable call.

Rosenthal nearing spring debut after live BP

JUPITER, Fla. -- Minutes after throwing 15 pitches in live batting practice on Wednesday, closer Trevor Rosenthal said he anticipates making his Grapefruit League debut by the end of the weekend.

Rosenthal was recently slowed by a groin strain but has not had any recurring issues since stepping back onto the mound on Monday. He threw a side session then before facing three batters in this latest test. All went smoothly, and Rosenthal finished the exercise with additional conditioning work and fielding practice.

"Everything felt normal," he said. "I feel strong. I'm excited. My schedule is normal now."

Rosenthal is in some uncharted territory as this marks the first time in his career that he has come into Spring Training knowing he'll pitch out of the bullpen. The 23-year-old right-hander threw 13 1/3 innings last spring, though five of those came when he was still a part of the starters' competition.

Rosenthal said that after taking into consideration his program from last spring and advice from guest instructor Jason Isringhausen, he would like to make "at least six or seven" game appearances this month. Last year, when the spring slate of games was longer and Rosenthal had no injury setback, he pitched in 10 games. None was on back-to-back days.

"Looking back at last year, I felt like that schedule was pretty good," Rosenthal said. "I feel pretty much close to game ready. I don't think we'll be too worried about back-to-back days, at least immediately. Hopefully, I'll have the same amount of opportunities to pitch as last year."

Worth noting

• Matheny said the organization still does not have an expected spring debut date for top prospect Oscar Taveras. The Cardinals continue to wait for Taveras to stop instinctively favoring the ankle that he did not have surgically repaired last season. Staff members sat down with Taveras to show him video that shows there is still some hesitation to push off his right ankle.

"He's anxious to get going, and that's exactly how we want him to be," Matheny said. "He's done a lot of work to get to the point where he is right now. In his mind, he's not favoring it. So it's a tough conversation. We're trying to do what's best for him. And what's best for our club, too, is to have a player who is completely ready to go before he goes out there and starts learning bad habits or makes himself more susceptible to an injury."

Taveras is scheduled to take the bus trip to Fort Myers, Fla., on Thursday.

• The Cardinals will keep center fielder Peter Bourjos off the field through at least Thursday as he deals with what Matheny described as right leg tightness. Bourjos last played on Sunday and alerted the medical staff to some tightness after coming out of that game.

"They're testing him out," Matheny said. "He has good strength, which is always the sign that we're not looking at anything major. But it was a little tender. We're just staying away from pushing him."

• The Cardinals and Marlins played a "B" game on Wednesday morning on one of Miami's practice fields. The Cardinals used the scrimmage to find playing time for several non-roster players participating in Major League camp. Four pitchers who recently participated in the organization's STEP (Spring Training Early Program) initiative -- Rob Kaminsky, Dixon Llorens, Michael Mayers and Scott McGregor -- appeared in the game.

• The Cardinals had a closed-door meeting with union chief Tony Clark and other representatives from the Major League Baseball Players Association on Wednesday morning. Clark and company wrapped up their visit to all of the Florida camps with the stop in Jupiter, Fla. He now heads to Arizona to meet with the remaining clubs.

Yadier Molina made his first start of the spring behind the plate on Wednesday. The Cardinals delayed Molina's first start as catcher in an effort to reduce the number of innings he catches this month. The organization's hope is that innings saved now will be innings Molina can add to his regular-season load.

• Reliever Jason Motte, who is rehabbing from Tommy John surgery, threw another high-intensity bullpen session on Wednesday. He continues to move closer to being ready to throw to batters in a live batting practice setting.

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.