Sauber: Young F1 pairing of Nasr and Ericssson 'delivering'

Little was expected of the duo this campaign in the wake of a 2014 season in which Sauber failed to score a point for the first time in its F1 history.

But Brazilian rookie Nasr and young Swede Ericsson, now in his second season after racing for Caterham last year, got Sauber on the board immediately with fifth and eighth in the opening race in Australia.

Points have been harder to come by since then, but despite that Kaltenborn could not be happier.

"They are absolutely fulfilling the expectations we had for their performance," she told AUTOSPORT.

"You can't have expectation as to points, but you can have expectation as to what they are delivering.

"They've adjusted to a new team, they're working closely with people, they have an understanding of the situation we are in.

"Importantly, they are highly motivated within the team, and the team feels that.

"They are very positive, they learn from their mistakes, are open to listening, are flexible, so I'm very happy with them.

"Of course they're young, they want to race and they want to show the world how good they are, but they're doing a good job.

"That's what they're here for."

Sauber's rise in form has been due in part to be being powered by a more competitive Ferrari power unit.

"The power unit is a very important factor in our performance, in what we did over the winter and what the team is showing now," added Kaltenborn.

"It has made the overall package. We are so much more competitive than last year, so I think they (Ferrari) have done a really great job. Hats off to them.

"Through them we are far more competitive.

"What the drivers complained about most was the driveability of the power train, and reliability.

"Both have been improved significantly. We have more power, we can see that, and of course we are now more reliable."