Mendy, 24, signed for the La Liga giants in July and heaps further pressure on Zidane’s squad after midfielder Marco Asensio ruptured his anterior cruciate ligament and winger Brahim Diaz suffered a thigh problem.
Newspaper AS reported Mendy, who cost the Bernabeu outfit a reportedly 50 million euros ($55 million), could miss up to four weeks.
Real have two remaining pre-season friendlies including Saturday’s game against capital city rivals Atletico Madrid in New Jersey before the La Liga season begins on August 17 with a trip to Celta Vigo.
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