Benzema was substituted in the 24th minute of Madrid's 1-1 draw, after overstretching in an attempt to control a pass.
Zinedine Zidane's much-changed side laboured to their second home draw of the season, as Lucas Vazquez cancelled out Ivi's surprise opener, with Marcelo dismissed late on to compound Madrid's frustration.
Reports in Spain have suggested Benzema could miss over a month and, while that has yet to be confirmed, he is almost certain to miss Madrid's UEFA Champions League opener against APOEL on Thursday morning AEST.
A Madrid statement read: "Following tests carried out on Karim Benzema at the Sanitas La Moraleja University Hospital, he has been diagnosed with a muscular injury in the semimembranosus of his right leg.
"His recovery will continue to be assessed."