Sauber's Pascal Weherlein has withdrawn from the Australian GP and has been replaced by Ferrari's Antonio Giovinazzi who will make his F1 debut.
Wehrlein sustained a back injury earlier this year following a crash at the ROC in Miami, and was sidelined for the first week of pre-season testing in Barcelona.
The German was subsequently cleared to take part in the second week of testing in Spain, and did not formulate any complaints about his form.
But Saturday morning in Melbourne he told Sauber he was doubtful of his ability to complete a full race distance at Albert Park, and preferred to stand down.
"My fitness level is not as it should be for a full race distance because of my training deficit. 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."
Antonio Giovinazzi, Ferrari's official reserve driver, has replaced Wehrlein and will make his Grand Prix debut this weekend in Melbourne.
The 23-year-old Italian is already acquainted with the Swiss outfit's new-spec C36, having been drafted by Sauber for the first week of pre-season testing.
Monisha Kaltenborn, the Hinwill-based outfit's team principal, is hopeful Pascal Wehrlein will be fit in time for the Chinese Grand Prix.
"We have great respect of Pascal's openness and professionalism," she said. "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."
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