PARIS — Surgery to repair a ruptured tendon in Ronaldo's left knee went well, but it is too early to say whether the Milan striker will play professional soccer again.

Following a two-hour operation Thursday, the three-time FIFA World Player of the Year was to remain at Pitie-Salpetriere hospital for eight days of physical therapy, with more treatment to follow in a specialized center, the hospital said in a statement Friday.

"It is too early to say what the chances are of Ronaldo playing competitive soccer again," the statement said. "That will depend not only on the surgery, but also on physical therapy and the motivation of Ronaldo — currently 31 years old — to return to high-level sports."

It would be at least eight or nine months before Ronaldo will be able to test his knee on a soccer field, the hospital said.

Dr. Gerard Saillant, who operated on a similar problem on the Brazilian's right knee in 2000, told L'Equipe sports daily that the operation "went well." Saillant also participated in Thursday's operation by Dr. Eric Rolland.

Ronaldo was injured in Milan's 1-1 draw with Livorno on Wednesday. He arrived at the Paris hospital on Thursday in the back seat of a car with his leg in a brace and an ice pack on his knee.

In comments broadcast Thursday, Milan president Silvio Berlusconi told Italian state television RAI that Ronaldo "fears for his career."

Milan coach Carlo Ancelotti told Italy's Gazzetta dello Sport newspaper that he was "convinced" Ronaldo will return to play "because soccer is his world and we are waiting for him."

"The first time he had this kind of injury, to his right knee, he recovered completely. I don't see why he shouldn't make it this time, too," Ancelotti said.

Ronaldo has battled serious injuries throughout his career, and has played sparingly since joining Milan from Real Madrid in January 2007.

Wednesday's match was only his fifth in the Serie A this season after injuring his thigh during preseason training on July 31. He returned in November, but has been in and out of the lineup due to a series of recurring problems.