The Rhinos' Super League crown goes on the line in the preliminary semi-final at Stade Gilbert Brutus on Friday, where the Dragons have become near-invincible in front of their passionate and vocal fans.
"Should we get this win, I think it will probably be on the back of our best performance of the year," McDermott said. "It will need to be. Whoever wins is 80 minutes away from the Grand Final so there's your motivation and you pretty much don't need to say any more than that."
Leeds' chances of remaining on course for a successful title defence have been dealt a major blow with the loss of prop Kylie Leuluai, who will sit out only his second game of the season because of suspension.
The Catalans, on the other hand, are set to be boosted by the return of fiery front-rower David Ferriol, who missed the Wigan defeat but will be out to make a big impression on his final home appearance as he prepares to retire to his vineyard.
Dragons coach Trent Robinson is also considering gambling on the fitness of former Bradford and St Helens stand-off Leon Pryce, who only started running a week ago after undergoing minor knee surgery.
Pryce has missed his side's last three matches and Robinson will not reveal his hand until an hour before kick-off but McDermott expects his side to face the former Great Britain star.
"If Leon is 50-50, he'll play. I can't see them resting him for this game," McDermott said.
"He loves getting the ball in his hands and taking on defences and I'm sure he'll be looking forward to doing that."
Pryce, who turns 31 three days after the Old Trafford showpiece, has the chance to become only the second player to appear in Super League Grand Finals for three different clubs. Lee Gilmour currently holds the distinction on his own after playing in title deciders for Wigan, Bradford and St Helens.