Fernando Alonso has described Nico Hulkenberg's drive to fourth place in the Korean Grand Prix as "superb".
The Ferrari driver spent the first part of the race behind the Sauber and could not overtake him.
Later in the race, Alonso was behind the Mercedes of Lewis Hamilton, who also failed to pass Hulkenberg.
"What Nico is doing is superb," said Alonso when asked about the German's performance.
"He is driving very, very well and he deserved to be in front of us because he did a fantastic race.
"[Sauber] were very good this weekend and they are doing a very good job.
"They were in the top three in qualifying at Monza as well, so they are on a high at the moment."
The Spaniard believes that the change in Pirelli's control tyres has played a part in Sauber's upturn in form.
Alonso said after the Singapore GP that the change in tyres was to blame for Ferrari's championship chances fading, but other teams have benefitted.
While Sauber's improvement is also down in part to a step forward made with a development package introduced at the Hungarian GP, its upturn in form has coincided with the change in rubber.
"When we changed to the 2012 tyres, there were some teams that had a penalty," he said.
"We can see very clearly that Force India now are fighting to take some points.
"Sauber was out of Q1 before and now it has both cars in Q3, so this is a benefit."