Steps forward were made with the C21's aerodynamics, floor, engine cover, front wing and weight reduction, but wind tunnel work ended in August as the team shifted its focus to the following year's C22.

The C21 proved quick in the early stages of the year, and Sauber was the fifth fastest team behind Ferrari, Williams, McLaren and Renault.

Both he and Massa also suffered electronic problems in Canada which caused them to exceed the pitlane speed limit and incur drive-through penalties as a result.

Massa also retired from several races after driver errors and collisions with other cars, most notably at the Italian Grand Prix.

Heidfeld was more consistent, only retiring from three races, but the C21 slipped off the pace in the latter half of the championship, and Sauber did not score any points in the final five grands prix.

The C21 was turned out in almost exactly the same livery as the C20; a blue, turquoise/teal and white colour scheme derived from sponsors Petronas and Credit Suisse.