Michael Schumacher's predicament in 2011 reminds Niki Lauda of the end of his own Formula One comeback.
The great Austrian retired as a double world champion in 1979, only to return three years later to face the young Alain Prost at McLaren.
Schumacher, the ultra-successful seven time world champion, also took a three-year retirement after 2006 and has struggled on his return with Mercedes.
"Now is the time when Michael must go as fast as Nico (Rosberg) in the same car, no doubt about it," insisted Lauda.
"If he can't do it, he needs to think about it. Just as I had to think about it in those days when the little Alain Prost came, I was able to win the title by just half a point because of my experience.
"The next year he drove me into the ground in the same car. Then I had the question: Am I still, as one from the generation before, still able to have the right performance?" he told the German broadcaster RTL.
"I realised that I could not. At some point Michael will have to realise the same," added Lauda.