With Michael Schumacher's difficult comeback season behind him, Alain Prost does not expect the seven-time World Champion to be back to full speed in 2011.
Frenchman Prost, who is one of F1's most successful-ever drivers behind 42-year-old Schumacher, said last year that the German targeting the title in his second career was "unrealistic".
Prost, 55, said Schumacher used Bridgestone's tyres as an "excuse" for his lack of pace, with "age" being the main factor.
Now, in a new interview with the Swiss newspaper Le Matin Dimanche, Prost said: "His decision to come back was personal and I respect it.
"I think it's impossible, at his age, to return to where he was in the past, but I hope he proves me wrong."
Prost said he does not miss racing in F1 because returning is out of the question, but admitted he would "like to do some laps in a modern car".
"But only to assess the developments in technology, which has always fascinated me," he said.
Driver Simulators Make Schumacher Sick: Report
Michael Schumacher's inability to work in a driver simulator hindered his preparation for Gands Pix in 2010.
That is the claim of a source close to the Mercedes driver, who told the Dutch website f1today.nl that Schumacher does not spend time in simulators because ever since a motorcycle fall in 2009 they have caused him to suffer from motion sickness.
On the other hand, the 42-year-old's teammate Nico Rosberg - who scored 70 more points than his famous cohort last season - is reportedly renowned for the time he has spent in simulators during his career.
"Nico spends a lot of time in the simulator preparing the car for the grand prix weekends," said the Mercedes source.
The source added that while Rosberg's setup work is "largely done" by the time of the first session on Friday morning, "Michael begins with a basic setting".
"This is one of quite a few very good reasons why Schumacher was sometimes at a disadvantage to Rosberg," added the source.
However, late last year Mercedes team boss Ross Brawn said he thinks Schumacher would have been more competitive in 2010 if Mercedes had a truly "top" driver simulator.
He said a new simulator is "currently under construction" at Brackley, but "it won't be fully operational before 2012".