Fremantle ended the home-and-away season with a perfect 12-0 record at Optus Stadium on the way to sealing the minor premiership.
But if it wasn't for a late Wharfie Time-inspired burst from Fremantle in round nine, Hawthorn would have walked away from the Dockers' home fortress with a win back in May.
Gunston was the key driver that night, with the 300-game veteran kicking five first-half goals mostly opposed to Luke Ryan.
Ryan was helpless to stop Gunston as Hawthorn pounced on Fremantle's turnovers to rapidly fire the ball into an open forward line.
Brennan Cox kept Gunston to just one goal in the second half, with his tactic of playing in front of the 34-year-old working a treat as Fremantle came from behind late to secure a 15-point win.
Cox will be absent from Thursday night's qualifying final at a sold-out Optus Stadium due to a calf injury, meaning the job to stop Gunston might fall to Ryan again, or perhaps Oscar McDonald.
Either way, Clark said it was imperative Fremantle don't repeat the errors they committed in round nine.
"Last time we played Hawthorn, we got it a lot wrong as a group," Clark said.
"It wasn't just the key defender playing on him (Gunston). It was probably the way we were moving the ball, the way we were defending the ground, which hung our key backs out to dry.
"Hawthorn have got some clear strengths, and Jack Gunston's one of many that they've got in their forward line.
"They've got Nick Watson, Jack Ginnivan, Dylan Moore, (Connor) Macdonald.
"There's threats all over that ground. It's not just about Jack Gunston."
Watson was also lethal that night, kicking three first-half goals before fading in the second half.
The 21-year-old earned his maiden All-Australian blazer last week after kicking 55 goals for the season, and Clark is well aware of the danger posed by the man nicknamed 'The Wizard'.
"It's probably never a thing about stopping 'The Wizard'. He's a pretty hard player to just completely take out of the game," Clark said.
"But nullifying him in ways we can is probably how we're going to go about it.
"He is a good player, and at times he's going to get stuff that goes his way, and he's going to do some spectacular stuff.
"As an opposition player, at times you do marvel at it. But if we can limit the amount of times he does that stuff, that'd be great."
