The young German is in Barcelona for the start of official testing, but still forbidden by doctors to drive after hurting his back in a January rollover crash.
“I haven’t had any pain for a long time,” he insisted on Monday.
However, Sauber ruled him out of action for the first of just two four-day tests, replacing him with engine supplier Ferrari’s reserve Antonio Giovinazzi.
“We will monitor his medical progress and then decide on the next steps,” said team boss Monisha Kaltenborn.
Wehrlein, 22, said in Barcelona that he will return for the second Barcelona test, but that decision has not yet been made formally.
“The next doctor’s decision will be at the weekend in Zurich,” he is quoted by the Swiss newspaper Blick.
“I hope they will say that everything is fine and I can be back in the car.”
Veteran correspondent Roger Benoit said Wehrlein denied that he has damaged some vertebrae.
He said his resting phase is simply precautionary.
“Health is the most important thing,” said Wehrlein. “I rely completely on the doctors’ advice.
“It hurts to watch, but I’m trying to get as much information as possible about the car and the tyres and get to know the team.”
He also hit back at claims that, even if he does recover in time for the second test, he will not be ready for Melbourne due to falling behind in his training programme.
“I’m not bedridden,” Wehrlein insisted. “I’m still training. And by the time of the race of champions, I had already gained five kilograms of muscle.”