Sauber's Felipe Nasr admits the team could struggle to remain competitive as its rivals begin introducing upgrades to their cars from the next race at Barcelona onwards.
After struggling though a torrid 2014 campaign and fending off Giedo van der Garde's legal advances on the eve of the new Formula 1 season, the Swiss team has surprised observers so far in 2015 with its form.
But, though Sauber currently lies ahead of several of its better-funded rival outfits in fifth in the constructors' standings, Nasr warns that the team may struggle to keep up its competitiveness.
"Barcelona will be a big turning point for the teams. Most of them will evolve their cars," the 22-year-old Brazilian told Globo.
"I don't know if we will be as close to the points places as we were in the first races.
"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."
Nasr, whose best finish of the year so far has been the fifth place he took in his very first race in Melbourne, added that future improvements by Sauber "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."