While Aaron Sandilands has declared himself a certain starter against the Cats at Patersons Stadium, doubts remain over the availability of clearance specialists David Mundy (ankle) and Michael Barlow (foot).
Fyfe, 20, and Hill, 21, have shouldered the bulk of Fremantle's midfield workload this pre-season, along with Greg Broughton and Hayden Ballantyne, and they will be key players against the reigning premiers on Saturday night.
Lyon said the highly-rated young pair needed to take the next step in their careers for Fremantle to have a successful season.
"If you look at the premiership teams of Collingwood and Geelong, they've got elite midfielders," Lyon said on Monday.
"Hill and Fyfe have done strong apprenticeships and are ready to start pushing up to those levels, as well as the injection of Hayden Ballantyne into the midfield.
"We really need those guys to become dominant midfielders. At the end of the year if we can talk about them in the same breath as [Scott] Pendlebury and [James] Kelly and [Joel] Selwood, we know we've had a successful year."
Mundy and Barlow have not played a match this pre-season, but Barlow completed strong training sessions on Friday and Sunday to push his claims for round one selection.
Captain Matthew Pavlich said Mundy, who trained on Monday morning, was still confident he would be fit to face the Cats, but he was behind Barlow in his preparation.
"I asked him how he was and he said he's right to go," Pavlich said of the 2010 club champion. "Whether that is for the Subiaco Lions or the Fremantle Dockers we're yet to see.
"We were always hopeful he'd be ready for round one but I think it's more likely he'll be elsewhere than running around in purple on Saturday night."
Pre-season star Clancee Pearce could be the big winner at selection this week, with Lyon declaring the rookie was "a really good chance" to face the Cats after an outstanding NAB Cup.
The fourth-year rookie can be upgraded to Fremantle's senior list for injured midfielder Viv Michie, who is sidelined indefinitely with a foot injury.
Pavlich also declared forward Jack Anthony a likely starter in a taller Fremantle forward line, with the former Magpie ready to revive his career after a disappointing 2011 season that saw him play just four games.
"He's had an enormous pre-season and he should have enormous confidence going into round one," Pavlich said.
"We're hopeful that he can get a game, because he's shown so much hard work and so much preparation. He deserves an opportunity."
Pavlich said there was a chance he would be called on to rotate through the midfield, with Mundy and Barlow in doubt and Anthony Morabito ruled out against Geelong.
However, Lyon reiterated that he planned to use his star goalkicker in attack as part of a three-pronged tall forward line.
"We'd like to spread the load," Lyon said. "Matthew will spend more time forward, [with] Kepler Bradley. Jack Anthony has had a super pre-season.
"We're certainly going tall with Zac Clarke running through there.
Last year [Chris] Mayne was really our second tall. This year he'll be about fourth in line. We're certainly taller."
