Manager Mike Redmond and hitting coach Tino Martinez were included in the group that took their swings off the hard-throwing 20-year-old.
"It took me three at-bats before I made contact," said Redmond, who retired as a player in 2010. "But I figured that was pretty good, because I hadn't had an at-bat in three years. It was fun. We had a good time.
"We made the most of it, coming in on an off-day. Tino got in there, and he had a couple of good at-bats against the kid."
Fernandez, ranked seventh on MLB.com's list of Top 100 Prospects, will make his first big league start on Sunday, against the Mets. The Marlins' first-round pick in 2011, he is making the leap from Class A to the Majors because Nathan Eovaldi and Henderson Alvarez are on the disabled list.
Tuesday offered a chance for Fernandez to see batters in a big league setting.
"He was probably nervous, saying, 'I don't want to square my manager up in the back with a 97,'" Redmond said. "Believe me, I was thinking the same -- 'I hope he doesn't hit me, I'm not ready for that.' We got in there and had fun. He threw me a couple of breaking balls and struck me out a couple of times."
Fernandez threw about 50 pitches on a chilly morning.
"It was fun. It was cold, man," Fernandez said. "When I was warming up, my eyes were like crying, it was so cold. But it was good to throw, because I'll be in New York."
Veteran Miguel Olivo caught Fernandez for the first time and came away impressed.
Olivo has been a teammate of some of the game's top pitchers, including Felix Hernandez in Seattle and Zack Greinke in Kansas City.
"He impressed me," Olivo said. "I had never seen a young talent like that. Like, 20 years old, throwing the ball with so much control, the breaking ball and the fastball. His fastball is really, really live. It's amazing.
"He can be better than anybody I have caught. He reminds me a lot of Zack Greinke with the fastball, slider and curve. I can compare him to him."