F1 drivers will lose wins due to 2017 cars, Rosberg believes

Rosberg retired from F1 at the end of 2016, five days after securing the drivers' title for Mercedes, just before the regulation change that has made cars faster and tougher to drive with beefed up aerodynamic and mechanical grip.

Hamilton has bumps and bruises from 2017 F1 cars

The German spent a day testing Pirelli's 2017 development rubber in a mule Mercedes last October, but has not driven the fully-fledged new cars.

Visiting the first pre-season test at Barcelona on the third day, though, Rosberg was impressed with the direction F1 has gone, describing them as "absolute monsters".

"It's such a massive hype at the moment," Rosberg said.

"So I wanted to see it first hand as well, see the new cars.

"They look absolutely monstrous, very very aggressive, and everybody's excited and that's great to see.

"The drivers are loving it, and I think this year they will be proper gladiators out there, with these cars, because the cars will take them to their physical limits.

"We might even see drivers losing race wins because of just being 'game over' physically - and that's what we need."

Asked whether the excitement of the new cars and the strong form of Mercedes with Lewis Hamilton and new recruit Valtteri Bottas made him regret the decision to retire at the end of 2016 at all, Rosberg brushed off any such suggestions.

"I expected [Mercedes] to be the best this year, because the team is awesome, yeah?" he said.

"I am not saying that that's the case, we still need to wait and see, but for sure it looks like they've done a great car - but that's not surprising.

"I'm really happy with my decision, you know, and I still love the sport, so it's great to be here, great to follow the action.

"The positive hype is awesome at the moment, you know, and I really hope the sport can progress, that would be cool.

"It feels good [being here], it's just very different, I'm very relaxed, I'm enjoying it."