"After the tests carried out on our player Arda Guler, he has been diagnosed with an injury to the left rectus femoris muscle," Real said in a statement.
The Turkey international returned early from the club's pre-season tour with a knee injury, for which he underwent surgery in August.
Guler returned to training a few days ago, but his latest injury has thwarted his anticipated debut against Las Palmas on Wednesday.
The club did not give details about his recovery, but Spanish media reported he could be out for three weeks.
Guler's injury comes on top of the recent absences of Dani Carvajal and Vinicius Jr, both with muscle injuries, while Thibaut Courtois and Eder Militao are expected to be out of action for the rest of the season with anterior cruciate ligament tears.
