Speculation is already mounting that Pascal Wehrlein could miss more than just the start of winter testing next week.

Following his violent rollover crash at the Race of Champions event a full month ago, the German has finally confirmed that he will sit out the first of the two four-day tests in Barcelona.

"I have to skip the first winter test due to medical advice because of a back issue," the 22-year-old German announced on Twitter.

"I feel sorry for the team but we'll come back stronger!"

Wehrlein, a Mercedes junior, has switched from Manor to the Swiss team Sauber for 2017, and he will be almost certainly replaced in Barcelona by Ferrari reserve Antonio Giovinazzi.

But whether he will miss the second test, or even the season opener in Australia, is now the subject of media speculation.

"Wehrlein could be missing for some time," said Auto Motor und Sport correspondent Michael Schmidt. "Because his injury also prevents him from training his neck."

Sauber is not commenting.

Schmidt explained: "The necessary neck training has intensified due to the markedly increased cornering speeds this year. And the longer Wehrlein is not training, the more muscle he has to build up afterwards. And the more his participation in Melbourne is endangered."

(GMM)