Nick Heidfeld is sure Red Bull and Sebastian Vettel will not walk away with the 2011 world championship.
The reigning champions enjoyed a dominant start to the season but German Heidfeld, who drives for Renault, has been particularly impressed with the improvements of the McLaren team.
"After the first races some people said it was going to be a walkover for Sebastian and Red Bull," he said in an interview with German broadcaster RTL.
"But if you look back on the past few years, something like that is really very rare. Particularly McLaren in recent years have often started a bit behind and then moved forward quite rapidly," added Heidfeld.
After the first races some people said it was going to be a walkover
Heidfeld said of McLaren: "If they have the development pace they've had in previous years, they will be a very serious challenger. And I hope that some other teams and us (Renault) as well can also be at the very front."