Fernandez, the 23-year-old ace who is scheduled to start on Saturday, began swinging in the cages for a couple of innings -- just in case.
"We talked about sending him home early," manager Don Mattingly said. "As the game unfolded, he kind of wanted to stay because he thought maybe..."
Fernandez became just the second Marlins pitcher to record a game-winning pinch-hit. Dennis Cook achieved the feat, also against the Braves, on Aug. 1, 1997.
"The game was going at a really fast pace," Fernandez said. "I said, 'I'm going to watch the game, stay here with the guys.' Then, we did the [double] switch, and I was like, 'Oh.' Then, they tied the game. Then I was like, 'I may want to go put my cleats on, just in case.' It was a long shot."
Protecting a 5-4 lead, the Marlins made defensive changes, replacing second baseman Derek Dietrich and first baseman Justin Bour. Chris Johnson played first, and Miguel Rojas came in at second.
When closer A.J. Ramos allowed the game-tying homer to Tyler Flowers to lead off the ninth inning, Miami was on the verge of running out of position players.
"You knew eventually something like that would happen," Mattingly said. "I think we've got to make sure because you can't really do that every day because you end up if it's a close game like that, you end up with nobody left."
Rojas got the 12th rolling with a one-out single off Casey Kelly, who entered the night the expected starter for Saturday. J.T. Realmuto walked and with two outs, Fernandez doubled.
"For me, it was pretty special," Rojas said. "I was talking to the [second-base] umpire [Alfonso Marquez] later. I was telling him, 'That's what a superstar does.' He's a guy who has been carrying a team from a long time ago."
Braves catcher Tyler Flowers said Fernandez benefited from a pitch that missed location.
"He didn't execute the pitch," Flowers said. "The previous pitch was more the game plan. Obviously, he's an athletic pitcher, and he can swing it a little bit. You know he's going to be real aggressive in that situation. We just had one get away and ran back close to the middle [of the plate]."
Fernandez is also eager to hit, but he didn't anticipate getting a chance.
"That's always been like a dream, to play in the outfield or to pinch-hit like that," Fernandez said. "But when it actually happened, I was like, 'Oh, my God, I'm actually doing this.' My heart rate started going faster. The main goal was trying to get a ground-ball hit somewhere, so we could get a run and go home."
The Marlins are so accustomed to Fernandez having success, he said his teammates in the dugout simply responded: "Oh, wow, shocker."