Stewart warns Schuey on greed

Schumacher is on target to take his fifth drivers' championship this year and increased his record number of wins to 57 at the Spanish Grand Prix. But three-times world champion Stewart believes the German should be prepared to walk away from the sport when he thinks the time is right.

"He is unquestionably the finest racing driver in the world today," Stewart told BBC Radio Five Live. "He could certainly have six [titles]. But I think it would be wise not to be too ambitious or, if you looked at it another way, too greedy.

"Life has been so good to him and so kind, he's been blessed in so many different ways that you shouldn't be asking for too much. You should at a point say this is just fine, it's nothing to do with money, or victories or numbers. It's to do with where you are and you've got to go on and do more with your life."

Stewart cut his own career short when he was at the top of Formula 1 in 1973. Having claimed his third title, the Scot quit with 27 wins to his name from just 99 races.

"You have to stop at a certain time or you do dribble on a bit and maybe wait too long and by then you've lost your shine," he said. "So I hope his timing is right."