Fremantle captain Nat Fyfe has hit out at recent speculation that suggested his future in the game was "done and dusted" after facing further fitness setbacks this season.

Former Dockers assistant Peter Sumich recently stated that ongoing shoulder issues had placed the two-time Brownlow medallist under an unpredictable injury cloud that could be "deteriorating really, really badly".

"He'd be nearly done and dusted if his shoulder can't come up," Sumich said on SportFM last month.

"I'm hearing he's having a lot of trouble with contact, can't even touch his shoulder."

Fyfe, who is currently sidelined with shoulder and back issues, responded to the speculation around his future by requesting any doubters to "go your hardest".

Speaking to 7 News, the veteran midfielder revealed that while some criticism and external pressure can leave an impact on players, the recent questions raised over his tenure are aimless.

"It works in funny ways, actually, the external commentary,” he said.

PERTH, AUSTRALIA - JULY 01: Nathan Fyfe and Michael Walters of the Dockers walk from the field after being defeated during the round 15 AFL match between the Fremantle Dockers and the Brisbane Lions at Optus Stadium on July 1, 2018 in Perth, Australia. (Photo by Paul Kane/Getty Images)

“At moments of vulnerability it cuts deep, and it feels like you’re lacking support, you doubt yourself.

“But most of the time, 98 per cent of the time, I absolutely love it because I just grab it and use alchemy to turn it into something that motivates me to get back into preparing and get back to my best.

“So for anyone out there who’s considering speculating on ending my career, please, by all means, go your hardest.”

Fyfe is expected to miss his side's Round 4 clash with Greater Western Sydney this weekend as the Dockers chase their third win for the season.

Senior coach Justin Longmuir will remain absent from his duties as he continues to undergo the AFL's health and safety protocols, while veteran David Mundy will return from isolation for Saturday's match.

Fremantle will be sweating on the fitness of fellow onballer Caleb Serong, who is currently nursing a knee complaint and missed his side's western derby win on Sunday.