The two outfielders are at Double-A Jacksonville. Yelich is expected to get the callup first, and that could come by the end of the month. Marisnick appears to need more time to refine his swing.
Ultimately, how they produce for Jacksonville will play into when they are brought up.
"A lot of that is dictated on how those guys are doing, and when we feel those guys are ready to come to the big leagues," Marlins manager Mike Redmond said. "We want to make sure the Yelichs and the Marisnicks are prepared to come to the big leagues. That's something that is ongoing, and we have discussions all the time.
"We want to make sure the timing is right. Yelich has been banged up this year. When we bring him, we want to make sure he is healthy and feeling good and confident. That's the most important thing."
Yelich, who went 2-for-2 with an RBI double in the Futures Game on Sunday, missed April with a right heel injury. And in early June, the 21-year-old went down with a strained abdominal muscle.