Michael Schumacher's former team-mate Johnny Herbert believes the seven-time champion will retire for good at the end of the 2011 season.
The German driver, who returned to Formula 1 last year following a three-year hiatus, has struggled to be as competitive as he was hoping for, often overshadowed by team-mate Nico Rosberg at Mercedes.
Schumacher endured one of his toughest races since his comeback in last weekend's Turkish Grand Prix, where he went on to finish in 12th position.
Herbert, who drove alongside Schumacher at Benetton during the 1994 and 1995 seasons, reckons the German will not continue racing after this year.
The Briton also believes Schumacher is still as good as he was, but is now racing against better drivers.
"The simple fact is that he is no longer the best driver on the track," Herbert wrote in a column in Abu Dhabi's The Nation newspaper.
"Schumacher has not lost any of his skill - the new generation of young drivers are just better than him. It is a case that the level required to win in F1 has gone up and he is not at that standard anymore.
"I do not think he is any slower than he was when he was winning seven world titles; he is just struggling to cope with a situation he is not used to - he is no longer the best guy in the field and he does not have the best machinery at his disposal, as well as the fact that he has a team-mate in Rosberg who is consistently beating him."
He added: "He did not return just to run in the middle order. His dream was to win again and make Mercedes race winners, but it has not turned out that way and I would be surprised if he chose to continue."