Sergio Perez says the degradation of this year's Formula 1 tires is a big concern, admitting he has been surprised by how weak the rubber is.
McLaren driver Perez developed a reputation for being easy on tires in 2012, but said the situation was too difficult at the moment.
"It's extreme. The degradation is very difficult. It's a big surprise," said Perez. "Normally in winter testing we see a lot of degradation, but never this much.
"We are going to have a race here so it's a bit of a worry. But we are still learning about the tires and I think once we go racing, things will change. I hope it changes, because if we are in this situation in Melbourne we are going to see something like seven or 10 stops."
The Mexican was quickest on day two of the Barcelona test on Wednesday, and he was at least happy to have managed to complete his program.
"The summary is positive. Today has been a very important day for us. We managed a lot of mileage and we completed the program, so I'm very happy in that respect. The conclusion is we have a lot of work to do before Melbourne.
"It's the same approach that we had when we started testing. We have to maximize every chance to make this car better before we get to Melbourne."
He refused, however, to draw conclusions about where McLaren stands at the moment.
"We have focused on ourselves. All we know as a team is that there is a lot of work to be done in the next couple of days. Where we are we don't really know. The car has a good base, but this base has to be improved for the first race.
"The team is working very hard to try to find more, and we need to find quite a bit more for the first race."