AC Milan striker Ronaldo suffered a thigh injury in training on Friday and is doubtful for Sunday's Serie A match with Fiorentina.
"His condition will be monitored in the next few hours. At this time his participation in Sunday's match between Milan and Fiorentina is in doubt," said a statement on the club's Web site (www.acmilan.com).
The game at the San Siro is important in the race for a Champions League qualifying spot. Milan are third and a victory would almost guarantee a top-four finish.
Sixth-placed Fiorentina also have an outside chance of making the Champions League places if they win.
Milan could also make next year's Champions League by winning this season's final against Liverpool in Athens on May 23.
Ronaldo missed Wednesday's semi-final second leg win over Manchester United because he was cup-tied.
