0119 GMT November 13, 2019
Isco's injury comes just two days after James Rodriguez also suffered a muscle problem, with Madrid already without Eden Hazard, Marco Asensio and Brahim Diaz due to various knocks, ESPN FC reported.
"After the tests carried out today by the Real Madrid Medical Services, our player Isco has been diagnosed with a muscular injury in the right femoral biceps," a club statement said.
The statement added that "his recovery will continue to be monitored" but several sources told ESPN FC that the Spain international could be sidelined for around three weeks.
Isco's injury is the latest in a long list that Madrid had had in recent weeks after Luka Jovic, Rodrygo Goes, Mariano Diaz, Thibaut Courtois and Ferland Mendy have also been sidelined.
Club sources told ESPN FC of "some concern" about the injuries, although they believe they are not directly related to the arrival of new physical trainer, Gregory Dupont, who joined this summer from the France national team to replace Antonio Pintus, who joined Inter Milan.
Isco will miss the match against Villarreal on Sunday and will not be available for Spain national team manager Robert Moreno ahead of the internationals against Romania and Faroe Islands on September 5 and 8.
In the best case, Isco would be ready to return in time to play against Levante on September 14, but club sources prefer to be cautious due to his past history with muscle injuries.