Felipe Nasr will get the new chassis he has been craving for this weekend's Russian Grand Prix.

The Brazilian has been complaining since the Melbourne season opener about braking instability aboard his Sauber, suspecting a chassis flaw.

"We can see in the data that I have a clear deficit in pace," he said on Thursday.

"The problem is that the car is unstable under braking, but I trust the team and am confident that we can solve the problems we are having."

It was earlier reported that Sauber's financial problems mean production of a new chassis had been delayed, but Nasr confirmed to the media that he will race chassis 3 this weekend.

There is no doubt, however, that money trouble is hurting the Swiss team, as reports emerge that a prominent engineer has left Sauber this week.

Nasr's teammate Marcus Ericsson admitted at Sochi that Sauber has fallen to the back of the field.

"We are now in the group with Manor and Renault," he said.

"In fact, we have the same car that we had in the second test in Barcelona - since then there have been no updates. We have developed some new parts, front and rear wing, but the question is when we will be able to install them on the car.

"We believe that when we do, it will be a step forward and we will be able to score points."

Sauber have yet to record a point in the championship so far.