ATLANTA -- In order to find their latest outfield replacement, the Cardinals bypassed candidates at higher levels in their system and instead zeroed in on Magneuris Sierra, who was still getting his feet wet with Class A Advanced Palm Beach.
A month after opening the season in the Florida State League, Sierra -- ranked as the Cards' No. 7 prospect by MLBPipeline.com -- was patrolling center field at SunTrust Park on Sunday. At 21 years and 30 days old, Sierra was the youngest Cardinals position player to make his big league debut since Miguel Mejia did it 10 days after his 21st birthday in 1996.
"I almost pulled out my hair because I was so happy [to be called up]," said Sierra, who recorded his first big league hit with a single off R.A. Dickey in the sixth inning of the Cards' 6-4, 14-inning win. "[I'm] thankful to God for the opportunity. I never expected this, but I've always been ready. I'm thankful to be here."

Sierra, who later in the sixth was picked off by Dickey, arrived at SunTrust Park before any of his teammates after taking a Sunday morning flight in from Florida. There was one more surprise in store for him when he walked in.
"He had no idea he was going to play today," said manager Mike Matheny, who plugged Sierra into the lineup's seventh spot. "That really made him light up. That was 10 years of Christmas morning all put together."
Sierra also showed off his glove on Sunday. According to Statcast™, Sierra covered 79 feet in 4.4 seconds to make a fly ball with a 35-percent catch probability look routine. In terms of catch probability, it ranked as the best catch by a Cardinals outfielder this season.
"I thought, for sure, that was going to be a gap ball," said Michael Wacha, the beneficiary of Sierra's catch. "That was a big out to start that inning. It just looked routine for him. That just shows what kind of speed and what kind of instincts he has out there."

The Cardinals added Sierra to their 25-man roster on Sunday while also transferring Jose Martinez (left groin strain) to the 10-day disabled list. The club has placed two outfielders (Martinez and Stephen Piscotty) on the DL since Thursday and have been without William Fowler since then, as well.
Martinez sustained the injury while trying to beat out a grounder to third in Saturday night's 5-3 win over the Braves at SunTrust Park. The Cardinals placed Martinez on the 10-day disabled list Sunday after flying him back to St. Louis for an MRI exam.

The fact that Sierra was already on the 40-man roster and can play elite-level defense made him the choice to take the open roster spot over more advanced outfielders Harrison Bader and Jose Adolis Garcia. With the likelihood that this will be a short-term stay for Sierra, the Cardinals preferred to minimize the roster maneuvering.
"This was a roster issue first and foremost, but I think it fit really well," Matheny said. "Let's give this kid a chance here. Anything he does offensively or on the bases is going to be a bonus. But for him to come out and play the kind of defense that we believe plays just as well in the National League as it does in the Florida State League, that is something that really kind of pushed us."
Sierra was arguably the most impressive defensive player in Cardinals camp at any position during Spring Training and left such a mark that a former Major League manager asked Matheny in March if Sierra would break camp on the Major League roster. Matheny had to inform him that Sierra, at that time, had never played above the Class A level.
"This kid just made a positive impression with how he handled a lot of different things," Matheny said. "I think you can be fooled in Spring Training in what you see in such a limited [time]. But you're not going to be fooled by skill set, and I don't think you get too fooled by how they handle different situations. He really did a nice job answering a lot of questions that we had."
Sierra, who was hitting .272/.337/.407 with seven extra-base hits and three stolen bases in 20 games for Palm Beach, is just the third 21-year-old position player to reach the Majors with the Cardinals in the last 22 years. Jose Pujols (2001) was the most recent. The last to make the jump from Class A Advanced to the big leagues was Mejia, though he did so under differing circumstances as a Rule 5 Draft pick.