Ronaldo registered twice in Saturday's 3-0 derby win at Club Atlético de Madrid, but damaged his left ankle as he tussled for a loose ball with opponent Luis Perea and forced the defender to turn into his own net for Madrid's third goal.
The Brazilian international, 29, underwent tests on the injury today and it was discovered he has a tear to the anterior ligament in his left ankle. Doctors estimate he will be sidelined for four weeks, ruling him out of both UEFA Champions League Group F meetings with Rosenborg BK.
Madrid right-back Míchel Salgado is another casualty of the capital derby. The Spanish international sustained a small tear to his left hamstring and must rest for ten days. Like Ronaldo and the suspended Sergio Ramos, the 29-year-old will sit out Wednesday's visit of Rosenborg.
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