Sauber driver Pascal Wehrlein has declared himself unfit for the rest of the Australian Grand Prix weekend, with Antonio Giovinazzi to replace him.

Wehrlein, 22, battled a back injury during pre-season, leading to him missing some of testing.

While he was cleared to race, the German has opted against taking his place in Melbourne, giving Ferrari reserve driver Giovinazzi an opportunity.

"My fitness level is not as it should be for a full race distance because of my training deficit," Wehrlein said in a statement on Saturday.

"I explained the situation to the team yesterday evening. Therefore, the Sauber F1 team has decided not to take any risks.

"It is a pity, but the best decision for the team."

Wehrlein struggled in practice on Friday, clocking the 18th fastest time in both sessions.

Sauber team principal Monisha Kaltenborn said: "We have great respect of Pascal's openness and professionalism.

"This decision was definitely not an easy one for him, it underlines his qualities as a team player.

"The focus is now on his fitness level, and in such a situation we do not take any unnecessary risks. Pascal will be in China as planned."