AC Milan are still trying to come to terms with Ronaldo's career-threatening injury that has shaken the club ahead of Saturday's clash at Parma.
The Brazilian striker ruptured tendons in his left knee in Wednesday's 1-1 draw against Livorno and 24 hours later underwent surgery in Paris.
'We're all very sad and worried about what happened to Ronaldo,' said AC Milan coach Carlo Ancelotti.
'I don't want to say his career is over because only time can put the word end to his career.
'From our part, we can only stay close to him. His team-mates left the stadium quickly to reach the hospital to check on his condition, I think it's the right way to stay close to a player who's suffering.
'Being close to him can help him cope at such a delicate moment of his career.'
Ronaldo, who is under contract with the Rossoneri until the summer, is expected to be out of action for at least nine months.
The 31-year-old has endured an injury-plagued campaign with a muscular problem having limited him to just six league appearances this campaign for the Rossoneri.
The news was a huge blow for Milan as the injury comes at a very delicate time in the season.
Milan travel to the Ennio Tardini Stadium this weekend looking to climb to fourth position in the standings before making the journey to London to face Arsenal in Tuesday's Champions League clash.
'It's a real shame,' added Ancelotti. 'Ronie wanted so much to play and to have a big say in this team.
'He has always worked with great seriousness and professionalism.
'He has always tried to make a contribution to Milan.'
Ronaldo's absence has added to Milan's injury problems, with 18-year-old striker Alexandre Pato and midfielder Clarence Seedorf both struggling with sprained ankles.
The only consolation for Ancelotti is that Brazilian playmaker Kaka and defender Alessandro Nesta are set to return to play on Saturday.
Kaka is expected to play behind Italian duo Alberto Gilardino and Filippo Inzaghi.
Having missed out on the chance to leapfrog Fiorentina in the standings, after their midweek draw, the Rossoneri will be desperate to come out triumphant against Parma.
Milan are fifth in the standings, one point behind Fiorentina, who hold the last Champions League qualifying spot.
Struggling Parma will be under pressure to get a positive result as they go into this weekend's encounter just one point above the drop zone having won just four games this campaign, all at home.
The Gialloblu have not given up hope they can spring a surprise come Saturday.
'On paper the game on Saturday is a tough one but it is in these matches that anything can happen,' said Parma defender Massimo Paci.
'We are in a position to win whether it is against the club at the bottom of the table or against Milan.'
The bad news for coach Domenico Di Carlo is that striker Cristiano Lucarelli has failed to recover from a muscle strain and Bernardo Corradi is also unavailable as he serves a one-match ban.