Schuey: I'll quit when I'm too slow

In an interview with AUTOSPORT's sister title Autocar, the world champion was asked what he'll do when young drivers such start to challenge him the way he hassled Ayrton Senna in the early 1990s.

"They're already doing it!" he said. "As long as I can compete with them, that's fine. But once I find out that I'm too slow then I will have to start thinking."

Schumacher, who will start the season driving last year's championship-winning car, reckons that the biggest threat to him becoming the first driver since Juan-Manuel Fangio to win three consecutive titles will come from Williams.

"My feeling is that Williams-BMW will be challenging us most - or maybe we'll be doing the challenging - simply because McLaren have gone over to Michelin tyres. I don't know what they have to learn by doing that."

A fifth world title would put Schumacher's name at the top of almost every list in the F1 record book, but despite his almost unparalleled success he has no intention of stopping just yet.

"That's why I never talk about statistics because very often is sounds like 'okay, I want to achieve that and once I have done it, there's nothing left to achieve' and that's not really the case for me."