Mark Webber believes that the tracks remaining on the Formula 1 calendar will make it more difficult for him to chase down World Championship leader Jenson Button.
Following Rubens Barrichello's triumph on the Valencia street circuit last week, Webber pointed to Singapore and Abu Dhabi as strong venues for the championship-leading team, adding that had the title run-in been held on tracks like Silverstone and the Nurburgring, where Red Bull was strong, it would be a different story.
Webber trails Button in the championship by 20.5 points with a maximum of 60 available, meaning that the British driver could need only two big results to make himself uncatchable in the championship.
"It's certainly not impossible, but it's going to be tough," said Webber on his title chances. "Looking at what happened in Valencia, we've got Singapore and Abu Dhabi as well. If we had the middle section of the races to the end of the year, we'd be saying we'll give it a little nudge. But it's going to be hard.
"It's not an excuse -- we capitalized when the tracks suited us. But there will always be pressure on the driver leading until he has won it."
The Australian added that the sensitivity of the cars to track conditions and configuration has played a big part in the fluctuation in form that has happened this season.
"It's venue dependent," said Webber. "That's why it is see-sawing so much. And the cars are sensitive to track temperatures.
"It is Brawn's to lose, we know that. They are the hunted and we have to gain a lot on them. We need a phenomenal amount of points and a very consistent run, and even then we need to have both of the Brawns to have a rough run to get to the top of the championship.
"It's not impossible, but as we know things can change fast. There are a lot of points to go."
Webber, who turned 33 yesterday, admitted that being in the hunt for the championship has made this the most enjoyable of his eight seasons in F1.
"I've had a lot of seasons in the past when the motivation is testing if the car is not reliable or quick," said Webber. "It's not enjoyable -- although it's nice to drive the car, it's not good to see the timesheets.
"This year has been sensational for me, with four podiums, some good finishes and more weekend's where we've extracted the most from the car.
"It's something that I'm very happy about. A lot of people said to me when I broke my leg that you are going to come out of this stronger. Maybe I have."