Sir Jackie Stewart has reiterated his belief that Lewis Hamilton is taking a risk as Mercedes could pull out of F1 at any time.
Mercedes returned to Formula One as a fully fledged works team back in 2010 when the purchased the Championship-winning Brawn GP outfit.
So far, though, their comeback has been anything but successful with Mercedes claiming just one victory in three seasons.
And should they again fail to deliver, Stewart fears that Mercedes' staying-power could be tested which could leave Hamilton without a race-seat.
"I think Ross Brawn is a wonderful man. I think Daimler Benz is one of the greatest companies in the history of motorsport," Stewart told Autosport
"But they have to win. The Silver Arrow has to win.
"Whether it was Stirling Moss and [Juan Manuel] Fangio, whether it was [Rudolf] Caracciola and the other great drivers of the thirties, when Mercedes were in the sport they had to win.
"And if they don't win, they get out.
"That's the risk. If for whatever reason, they do not win, it's a five-minute board meeting decision with a bunch of people on the board who are not passionate about motorsport.
"They like the results if they win. If they don't win, it's yesterday. And that takes five minutes.
"If you were looking at it in a conservative fashion, you'd say 'I've got to stick with McLaren because I know they're always going to be racers'. They will never be out of motor racing."