Jenson Button has tipped both Ferrari and Mercedes to give McLaren a hard battle in qualifying for this weekend's Canadian Grand Prix.
McLaren have been the biggest challengers to Red Bull so far in 2011 and sit second in the constructors' championship, with Lewis Hamilton being the only driver other than Sebastian Vettel to have won a race this season.
Red Bull have however been easily the team to beat in qualifying with a 100 per cent record this season and although he feels McLaren will be closer this weekend, Button warned that the team couldn't focus too much on Red Bull and needed to be aware of the challenge from behind.
"Qualifying will be pretty tricky," he was quoted by ESPN
. "I think we'll be a lot closer to Red Bull but you have got to look at what Ferrari have got with the DRS. We seem to be able to use it in a lot more places than some others, but Ferrari and Mercedes can get 20km/h from their DRS, whereas a lot of teams are more like 12km/h.
"They are going to be very quick. They will be our biggest competitors here, which I think is a bit of a surprise to a lot of people."