Barcelona could be a "turning point" in Sauber’s 2015 campaign, driver Felipe Nasr has admitted.
Having struggled financially through 2014 and then fended off Giedo van der Garde’s legal advances in Australia, the Swiss team has surprised so far this season with its pace and results.
And Brazilian rookie Nasr, 22, has been the star, delivering most of the points that have powered Sauber to fifth in the constructors’ standings.
But after returning to his home city of Brasilia in the lull before the start of the European season, Nasr warns that Sauber may struggle to keep up its top form.
"Barcelona will be a big turning point for the teams," he is quoted by Globo. "Most of them will evolve their cars.
"I don’t know if we will be as close to the points places as we were in the first races," admitted Nasr.
"It will be a great test for us to know where we’ll be, but realistically, we knew that things would get more difficult during the year," he added.
Much of the credit for Sauber’s resurgence has gone to engine supplier Ferrari, and Nasr confirmed that an update from the Italian marque is expected in Barcelona.
"And the improvements from Sauber," he added, "will be mainly on the aerodynamic side.
"We had a new front wing in China, but unfortunately it did not work as we expected. So it is being redone for Barcelona and we hope to get something out of it."