Ferrari, which bused in scores of fans from Italy and France to the hospital in the Alpine city of Grenoble, put a message on its website, saying “Forza Michael”, or “Go Michael” in Italian.
“He is tackling the most important fight of his life and, therefore, we want to send him very special wishes,” said Schumacher’s old team, as similar messages poured in from around the world.
German former tennis ace Boris Becker wished his compatriot “Happy Birthday” on Twitter, adding “Fight Schumi” in a German hashtag.
The seven-time world champion slammed his head against a rock on Sunday while skiing in the French Alps and has had two operations to remove bleeding and pressure on his brain.
He is being kept in an induced coma and, in the latest update by his manager on Wednesday, his condition was described as stable but critical. His family is at his side, including his wife, Corinna, his two teenage children, his father Rolf and brother Ralf, who is also a racing driver.
“Following Michael’s skiing accident, we would like to thank the people from all around the world who have expressed their sympathy and sent their best wishes for his recovery,” the family said in a statement.
Fans left a poster outside the Grenoble hospital saying “Schumi, all our thoughts for you and your family”.
“He is one of my greatest idols. We want him to fight and to return to us,” said French fan Gabriel Klose.
However, the Ferrari tribute has created controversy, with some accusing the Italian racing giant — which asked fans to sport its trademark colour red and its insignia — of exceeding the limits of good taste.
Roberto Luongo, president of the Roma-Colesseo Ferrari club, said he did not want to be associated with an event linked to “a man who is suffering”.
Schumacher’s fan club in his childhood town of Kerpen said any celebration of the birthday would be in bad taste.
There have been conflicting statements about the speed Schumacher was going when he crashed in the upmarket Meribel ski resort, where he has a property. The impact as he hit a rock split his helmet in two, according to a source close to the inquiry.