"Right now, we're going to keep the kid [Turner] in the rotation, and we're going to put LeBlanc in the bullpen," Guillen said. "Then, maybe, depending how we pitch, go with a six-man rotation. It depends on how those guys are going. It depends if we're going to need them.
"We want to see those two kids throwing, and that's the reason we're doing it that way, because we want to see them."
Turner is one of the most highly touted prospects in the game. The right-hander was acquired from the Tigers on July 23 as part of the Omar Infante/Anibal Sanchez trade.
Turner made his Miami debut in the first game of Wednesday's doubleheader at Arizona. He suffered the loss, giving up three runs in six innings.
The Marlins obtained Eovaldi from the Dodgers on July 25 as part of the Hanley Ramirez trade. The 22-year-old started on Friday against his former team.
LeBlanc, meanwhile, is a 28-year-old who has impressed since Spring Training. The lefty has been caught in the numbers game before. He didn't make the Opening Day roster, and when he joined the club on July 1, it was as a reliever.
LeBlanc made 11 appearances in relief, posting a 1.15 ERA in those outings. He replaced Carlos Zambrano in the rotation, and is 1-2 with a 3.29 ERA in five starts. LeBlanc suffered a hard-luck loss in Game 2 at Arizona on Wednesday, giving up three runs (two earned) in seven innings.
The Marlins could go with a six-man rotation, making LeBlanc a starter again, beginning on Aug. 31, when the team has a string of 13 straight games. However, that may not be the most practical option, because LeBlanc would again have to build up to throw multiple innings after he was asked to scale back.
Guillen added that the organization is high on LeBlanc, who is expected to be a frontrunner to make the 2013 roster.
"We've loved that kid since Spring Training," Guillen said. "Is he going to be on the team? Yes. Where? We've got to wait and see how that thing works out in Spring Training."