Matt de Boer will become Fremantle's fourth debutant this year when he runs out in Saturday's western derby at Subiaco Oval.
"It's a big occasion for him," Fremantle coach Mark Harvey said.
"He's a product of WA football, coming from grass roots, playing at Claremont, being on the rookie list and now playing his first game for Fremantle against West Coast.
"He's got a more seasoned bodies than a lot of other guys we've got just out of the side at the moment.
"He's got a good temperament and he's got this exciting nature about him that can really enthuse the side.
"I'll ask him to fill a role and hopefully he can do that.
"Every club goes through injuries but when you lose one of your star midfielder like Rhys it can be difficult so it puts pressure on other guys to fill the void in that area."