"With their line-up and match fitness at the moment, they're capable of playing their best footy all year," he said.
"We realise that and we've let the players know it's going to be difficult to win the game."
Thompson said the Cats have plenty of work to do after their two-point loss to West Coast at Subiaco on Saturday night, rejecting Magpies coach Mick Malthouse's claim that Geelong was currently one of the league's best teams.
"If you look at last week, we're not one of the form sides of the competition," he said.
In recent Cats-Magpies clashes, Anthony Rocca has caused the Cats coach plenty of head-aches, something that won't change on Friday night, Thompson said.
"We've got to do our best to keep him down, he's had ankle problems but saying that he's kicked goals against us and we have to stop him."
Thompson said Tom Harley and Matthew Scarlett will play on dangerous forwards Rocca and Chris Tarrant, but it was not revealed who would mind whom.
James Kelly, whose season is over after he broke his left leg in the first quarter against the Eagles, will return home on Thursday, Thompson said.
"He's looking forward to pre-season training, he's in very little pain now and just wishes us all the best."
The Cats trained in doors at Altona on Wednesday, in preparation for their under-the-roof match at Telstra Dome.
Remarkably, every side to have trained at the Westgate Indoor Sports Centre has won the following weekend, which provided the Cats incentive to return there after they accounted for the Bombers in round nine.
"That's why we came here," Thompson said.
