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Reigning world champion Sebastian Vettel is wary that Mercedes's strong straight line speed will be a crucial factor at this weekend's Canadian Grand Prix.
The German won the Canadian Grand Prix in 2013 but fears that Red Bull could be in for a difficult time this weekend.
"This year we are a bit down on power still so it will be difficult to match the Mercedes powered cars down the straights," he said.
"But there are also some corners here and they’ve been good for us – we were in a good position in 2011 to win the race and we won here last year. I think we have reason to be confident but we know that [it won’t be easy]."
"Obviously we know they [Mercedes] have a very strong package a strong car and strong power unit. How exactly it will pan out is difficult to say. We have to look after ourselves and do our best. The corners are very tricky and demanding here and you can make up a lot of time in the corners. Of course we will try and do our best down the straight but we’ll try at the corners."
Vettel reckons that Red Bull has made progress with the Renault power unit since the start of the year but remains wary that there is work to do.
"If you talk purely about the engine then I think we made a lot of progress since winter testing," he said.
"The engine is drivable, generally in wet conditions for example where it's more crucial we've done pretty well
"We’re not yet where we want to be especially in corner entry and on the brakes but I think we will get there."
