Geelong have been rocked in their preparation for the AFL preliminary final against the Brisbane Lions after assistant coach Steven King collapsed at training.

King, who is one of the leading candidates for West Coast's head coaching position, was rushed to hospital after what Cats officials described as a "medical episode" at GMHBA Stadium on Friday morning.

The 45-year-old collapsed on the field while talking to colleagues and players at the start of the light training session and was quickly tended to by club medical staff.

Geelong coach Chris Scott later said the club believed it was not a life-threatening situation, and King was conscious and breathing normally before being taken to hospital.

King remained under observation on Friday and is expected to recover, but is unlikely to be part of the Cats' coaching panel in the knockout clash with Brisbane at the MCG on Saturday.

"For us to prioritise his health, it would be irresponsible for us to even consider him to be around over the next 24 hours or so," Scott told reporters about an hour after the incident.

"I'm led to believe that there is a chance that he could get a clean bill of health really quickly, but out of an abundance of caution it just seems logical to us and the right thing to do.

"In these situations it does reinforce that there is a right thing that supersedes football.

"I suspect that if he's feeling good he'll be disappointed to hear that news and even if he's not feeling great he'll be disappointed because he's a competitor.

"But even at this pointy end of the season it reinforces to us what the right thing is over lesser priorities."

King's episode occurred at the start of Geelong's final light training run in preparation for Saturday.

Players were quickly called into a huddle and left the training track within minutes while medical staff tended to King.

Assembled media were also asked to leave, allowed to return when players re-emerged to complete the training session about 30 minutes later.

"It's upsetting and it has an impact on the players," Scott said.

"I don't take the view with these things that you've got to pretend that something isn't happening. What we've got to do is just deal with where we are.

"Again, the feedback's really positive, so we will do our best to focus on that positive, but it is quite confronting."

King had been in Perth for an interview with West Coast and returned to Geelong on Thursday night.

The former St Kilda, Western Bulldogs and Gold Coast assistant is one of three remaining candidates on the shortlist for the Eagles job, along with Melbourne assistant Andrew McQualter and Collingwood's Hayden Skipworth.

Scott said King's workload had "possibly" contributed to the medical episode.

"He is a workaholic but I don't think it would be prudent for me to speculate as to the causes," Scott said.

"He has been working pretty hard and it is a stressful situation to be at this point of the season full stop.

"But when you add in there is a bit of stress and excitement at the prospect that he could be facing over in Perth.

"I've only really known him well for 12 months but he's a very resilient character. I'm confident he'll bounce back."

King played 240 AFL games in a decorated career with Geelong and St Kilda, including the Cats' drought-breaking 2007 premiership, before moving into coaching.

He was the Suns' interim coach late last year and returned to Geelong as senior assistant to Scott this season, looking after the Cats' midfield.

West Coast released a brief statement on Friday, saying the club's thoughts are with King, his family and Geelong.

"Steven's health is the priority, and we wish him a speedy recovery," the statement said.

Geelong experienced tragedy in February 2021 when legendary club volunteer Vic Fuller collapsed at training and died.

Fuller, who was 79 years old, suffered a stroke during training and could not be resuscitated.