Marcelo was forced off injured against Sevilla on Wednesday night, making him another injury doubt for head coach Julen Lopetegui ahead of the crucial Madrid derby on Saturday.
The left-back pulled up abruptly in the 72nd minute with a non-contact injury and hobbled off the field of play.
The Brazilian’s premature departure left Real Madrid down to 10 men for the final stages of their 3-0 defeat to Sevilla at the Estadio Ramon Sanchez Pizjuan, having just replaced Luka Modric with Dani Ceballos in their final change of the match.
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"Marcelo seems to have a [muscle tear] but we'll have to wait for tests tomorrow," Lopetegui said after the match, while the defender himself confirmed that the injury was to his calf muscle.