Mitchell had a scan on an unspecified complaint last Monday afternoon and there were some queries over his fitness during the week.
The 31-year-old missed the round two match with Essendon with calf tightness, but he should play in the clash of the unbeaten sides at the MCG on Monday.
"His fitness test will be training, so if he gets through training he should play," Clarkson said before training on Sunday morning.
Mitchell did everything that was asked of him thereafter as the Hawks went through a 50-minute touch session in the lead up to Monday's huge game.
The star midfielder coasted through the Hawks' full-ground ball movement drills and their handball specific 'grid games' during the session.
While Mitchell is a near certain starter, the Hawks have decided not to rush defender Brian Lake back to line up on Geelong spearhead Tom Hawkins.
Lake missed the first three matches because of suspension and played 100 minutes of game time in the VFL on Saturday night, following a return through the reserves a week earlier.
"It's always tempting because Lakey's available. It's really important that we get proper match conditioning into Brian," Clarkson said.
"He missed three games of footy and he had a bit of calf complaint in that time as well, so it was important that he got some game time."
"He'll be back in the mix more next week, but he still may require another game in the VFL yet."
Geelong has famously won 11 of the past 12 clashes between the sides, with their streak ending in a thrilling five-point Hawks win in last year's preliminary final.
Clarkson said the Hawks have got some unfinished business against the Cats.
"We're well beneath where we want to be in terms of the last 11 encounters that we've had against this side," he said.
"We've got some ground to make up, simple as that.
"We rate ourselves a hell of a lot better than losing to the Cats 11 times in a row."
Hawks midfielder Mitch Hallahan has been named to make his senior debut, the club's fourth debutant this season.
The 21-year-old midfielder was drafted by the Hawks with pick No. 38 in the 2010 NAB AFL Draft and Clarkson said he had earned his opportunity to play in what shapes as one of the biggest games of the year.
"He's done some hard yards," Clarkson said.
"He came to us in his first couple of years (and) he had some ankle troubles and he didn't get up and going for a couple of years.
"But he's played some really good footy for the last 18 months. He's ready to play, he has been for some time but it was just hard to get him into our side."