Pascal Wehrlein is confident he will be fit enough to race at the Chinese Grand Prix after opting to sit out the Formula One curtain-raiser in Australia.

Wehrlein suffered a back injury at the Race of Champions in January following a collision with Felipe Massa.

The young German missed the opening week of pre-season testing as a result but was able to return and get some laps under his belt ahead of the first race in Melbourne.

He drove his Sauber during the practice sessions on Friday but opted not to participate 24 hours later, his place taken by Antonio Giovinazzi - who qualified 16th.

Wehrlein insisted his absence was merely due to a lack of fitness rather than further issues with his back and expects to be ready to have his first competitive outing for Sauber on April 9.

"Anyone who knows how ambitious I am will know how much this decision hurts me," he said. 

"Especially since I'm having no pain. I just realised in the long runs that my fitness is not enough for 60 laps.

"The decision was made between myself and the team. The doctors were not involved.

"I've been in the car for four days now [since the injury] and I've been feeling better every day.

"Next week I will continue to improve. I'm going to train hard in Europe next week, and I'll be back in the car in China on Friday. Then we'll see."