If he was in charge at Lotus, Gerhard Berger would not have signed Kimi Raikkonen for 2012.
Former ten-time winner Berger, the former BMW motor sport director and Toro Rosso co-owner, admitted that the 2007 world champion's comeback is "good for Formula One".
But "If he is able to reach the top again I would say is 50-50," he told the Austrian broadcaster ORF.
"I do not think the best," said the former Ferrari and McLaren driver, "if he decides to stop, does a bit of rallying and then says 'Ok, now I'm coming back'.
"I would be surprised if he has the strength, discipline and ambition to return to the front," added Berger.
"Of course he should not be underestimated and I do not -- there is no question he is quick and it would be good for F1, so let's hope for it and wish him all the best."
But if he was in Lotus chief Eric Boullier's shoes, "Clearly, no, I would not have taken him", admitted Berger.
There is no question he is quick and it would be good for F1
"Formula One is so unique. If you don't really live it day and night, constantly perfecting yourself and working on it, it is difficult," he added.
"It's hard, hard work, and whether he has the willingness to do this hard, hard work, we'll see."
Berger's fellow Austrian, triple world champion Niki Lauda, told Salzburger Nachrichten newspaper: "It's cool that he is back.
"He (Raikkonen) is a colourful personality and will arouse great interest among the fans and the media."