Red Bull’s rivals see Canada as an opportunity to end the winning streak.
Sebastian Vettel, who has won the last three grands prix on the trot and also two of the other three races so far in 2011, admitted to Sport Bild on Thursday that the Circuit Gilles Villeneuve is "not our track".
"This will be one of our most difficult weekends," he said.
McLaren is usually strong in Montreal and Red Bull also bungled the strategy a year ago.
"I think we have learned our lesson," said German Vettel, but his teammate Mark Webber is also concerned the RB7 might not get a chance to shine so brightly this weekend.
"There are only slow corners, many straight lines, and we drive with less downforce than usual," said the Australian, explaining why Red Bull could be weaker in Canada.
"The straights are not ideal for us, but there are also places where we will be good," predicted Webber.
Ferrari’s Fernando Alonso says it is too early for the Italian team to think about beating Red Bull on merit, but he is watching the weather forecasts for this weekend with close interest.
"I would have no problem with rain," said the Spaniard. "Anything that deviates from the norm can only improve our situation."