Fremantle senior coach Ross Lyon said he would defer to the experts when it comes to the decision on Nat Fyfe’s availability for this Saturday’s RAC Derby at Optus Stadium.

The Fremantle captain had to be helped from the field during the third term against St Kidla at Optus Stadium and was ruled out of the rest of the contest.

Lyon said it was not up to AFL coaches to decide if a player is fit to return from concussion.

“Ever since I’ve been involved (in football), it’s always been the doctor’s call,” Lyon said.

“As a coach I defer to the experts and there’s a clear process.

“I understand it’s a hot topic throughout world sport and everyone is going to have their opinion. I’m not here to engage those, I just defer to the experts and the protocol and back that in. 

“My feeling is that I have genuine care, as everyone has for Nathan and all of our players.

“It’s really dangerous for me to put my fingerprints anywhere near this because I’m no expert and there’s a clear mandated process and protocol that we’ll step through with (Fyfe’s) best interests.”

Fyfe only has a six-day break to recover from the heavy head clash with Josh Battle and Lyon said the midfielder was in good spirits.

"He texted me (today) just to say 'G'day' and said 'I'm progressing pretty well'," Lyon said on Tuesday.

"(I) understand there's been huge focus on Nathan with his concussion. There is clear mandated AFL process and protocol to step through.

"Our medical team are all over that, and I'm certain that will progress throughout the week.

"I spoke to him after the game twice. He was in pretty good spirits, really.

"Yesterday was a player's day off, he slept well, felt pretty good. You need to be symptom-free and then undergo the (cognitive) test and pass that.

"As we jump through those hoops, we'll know more then, but that's basically all I've got for you."

Lyon said if Fyfe passed the cognitive state test this week and was made available, it would ultimately be Fyfe’s call whether to take the field. 

"Clearly, at the end of the day it's the player's final decision, but it's binary 'yes' or 'no' whether you're available and then the player can make the final call as they always do," Lyon said. 

Fyfe missed the 58-point loss to West Coast in round 20 last year due to a hamstring injury, and his absence this Saturday night would be a blow to the Dockers' hopes.

Reece Conca and Andrew Brayshaw helped cover Fyfe in the midfield against the Saints, and Lyon declared Fremantle needed to look within the team's flexibility if the skipper was ruled out.

Young midfielders Mitch Crowden (32 disposals), Tom North (26) and Stefan Giro (24, one goal) performed strongly for Peel to also put their hands up.

Prized recruit Jesse Hogan spent the Saints clash in attack and shapes as another option to move into midfield.

Hogan picked up 21 touches in his Fremantle debut against Gold Coast mainly running through the engine room.

"He's an option. On the weekend, he was forward the whole game, so that's reasonably settled," Lyon said.

"I thought he impacted, he's been selfless. It takes time to build a chemistry,” Lyon said. 

"(West Coast spearhead Josh) Kennedy is a 31-year-old player with those midfielders, so it takes time to build that up and Jesse is going to be judged over seven or eight years."

Sean Darcy is expected to be fit after battling a corked quad, but Lyon stopped short of declaring he would return to lead the ruck, shifting Rory Lobb back to attack.