JUPITER, Fla. -- Watching Sandy Alcantara throw off the mound just once is all the Marlins needed to see they have a potential ace. But at this stage, Miami's staff also recognizes the importance of handling the 22-year-old's development with care.
So, if there are any questions as to whether the rangy right-hander (he's listed at 6-foot-4, 170 pounds) with an upper-90s fastball is completely ready to be a fixture in the rotation, Alcantara may open the season at either Triple-A New Orleans or Double-A Jacksonville. His performance in Spring Training ultimately will decide.
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"That's the one thing you never want to get away from," manager Don Mattingly said. "You know there is opportunity here, and you know there's a guy with a lot of talent. But you want him to be good for a long time. So you worry about development first, and for him to be prepared to have success."
Alcantara is the Marlins' No. 3 prospect, according to MLB Pipeline. The Dominican native was a centerpiece in the Marcell Ozuna trade with the Cardinals. He debuted as a September callup with St. Louis last year, tossing 8 1/3 innings of relief.
"I was able to pitch in September in the big leagues," Alcantara said in Spanish. "I've got to work at it to get back up here and take advantage whenever they give me the ball."

Alcantara's first bullpen session was on Wednesday, Miami's first day of Spring Training, and he's expected back on the mound on Friday. Alcantara's four-seam fastball averaged 98.21 mph last year, well above the MLB average of 93.21 mph. The Marlins envision him as a starter, and if he can command his breaking pitches, he projects as a top-of-the-rotation-type talent.
"The experiences I got from last year told me I need to keep working on my breaking pitches, the command on my breaking pitches," Alcantara said. "And I've got to attack the hitters with my fastball."
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Mattingly says the only two locks for the Marlins' rotation are Dan Straily and Jose Urena, though a third spot also could be relatively secure: Mattingly noted on Thursday that left-hander Jarlin Garcia, who pitched in relief last year, is being stretched out to start. Alcantara is one of about 10 candidates to fill out the rotation.
Pitching coach Juan Nieves studied video of Alcantara in the offseason, and early in camp, he will be monitoring each throwing session. But there won't be any rush to push Alcantara if he's not completely ready.
"I think we're in a situation where we must not have to speed up any processes," Nieves said. "It takes time."
The Marlins learned the hard way a few years ago with Brad Hand, who ran out of options and was let go. The Padres picked him up, and the left-hander became an All-Star closer last year.
"When you speed up guys to the big leagues, you pay the consequences either way," Nieves said. "Either guys that leave, because options are out, or guys who don't grow in the big leagues and aren't able to stay or become solid players or pitchers in the big leagues. So, we're going to try. I'm sure everything will be on time."