Right now, he's at 104 2/3 innings in 18 starts prior to the All-Star break. Fernandez will make his first post-break appearance on Tuesday at Colorado.
"We're going to use him the way we have," manager Mike Redmond said. "We're going to use him the way we have the whole year until those innings dry up. If he has a chance to pitch late in the game, he's going to pitch late in the game."
The simple formula is for Fernandez to average six innings over 10 starts in the second half. That would get him to 164 2/3 innings.
But Redmond added the Marlins will not necessarily put the brakes on any start in which the rookie could go longer than six innings.
"We're not going to pull him out early because we want to save his innings," Redmond said. "In every one of his starts, we're going to try to win. Based on how he throws and how his pitches are, and how his innings look, or how his pitch count is during the game.
"If he's able to throw seven or eight innings, he's going to throw seven or eight innings until he reaches that mark."
The Marlins are closely monitoring their hard-throwing right-hander, who turns 21 on July 31.
Fernandez made the leap to the big leagues without pitching higher than Class A. A year ago, he threw 134 innings total between Low A Greensboro and Advanced A Jupiter. And he reached the big leagues with 138 1/3 Minor League innings, counting 2011.
The Marlins aren't planning on skipping starts over the next few weeks in order for Fernandez to pitch into late September.
"We'll find out exactly where that mark is as we go," Redmond said. "I'll think we'll stick to that."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter