Alain Prost says he understands Michael Schumacher's desire to return to Formula 1, but believes the seven-time world champion made the right decision in calling off his comeback due to worries over the strength of his neck.
Schumacher injured his neck in a motorcycle testing accident in February and after testing a 2007 Ferrari decided that he was not fit enough to race again in F1.
Prost, who won four world titles between 1985 and 1993, told French newspaper Le Parisien that he believes Schumacher needed more time to prepare himself for a return.
"The desire and motivation to return takes time to disappear, it takes several years to abandon F1," said Prost. "Michael and I hung up our helmets for different reasons, but when you were competitive the temptation to return when asked is great.
"If there was any physical risk, Schumacher was right. The neck is crucial in motorsport and if there is pain you can quickly feel nausea and have impaired vision."
Prost also questioned whether the German's decision was made at least partly because of question marks over his performance.
"It remains to be seen if Schumacher stopped solely because of the health problem, or because when he resumed driving he realised that the task was enormous.
"He has not started in F1 for three years and only had three weeks to prepare. The body changes very quickly when you stop racing, a driver does not react the same way and the vision is not as sharp. When I returned in 1993 after eight months it was very difficult to find the best level, Schumacher may need more time.
"In 1994 McLaren asked me to take the wheel. I conducted three days of testing and I immediately realised that something was broken. The speed was there, but not the will to manage the pressure, travel and media that comes with a championship contest.
"A year later, Jean Todt suggested that I become team-mate to Schumacher to help him become champion at Ferrari. I would have been clearly number two, which was ok - I almost drove, but finally I did not, for the same reasons."