Kylian Mbappe suffered a thigh injury during Real Madrid's 3-2 victory over Alaves in La Liga on Tuesday night.
Mbappe, who scored in a fifth straight match to put his side 2-0 up five minutes before half-time at the Bernabeu, was replaced by Arda Guler in the 79th minute after seemingly feeling some discomfort.
A Real statement on Wednesday read: "After the tests carried out today on our player Kylian Mbappe by the Real Madrid medical team, he has been diagnosed with an injury to the (left thigh)."
No further information was disclosed as to the expected timescale of Mbappe’s recovery, but reports suggest the France captain will be sidelined for three weeks.
Mbappe, who signed a five-year deal with the Madrid club in July after his contract at Paris St Germain expired, has made an impressive start to life in Spain.
The 25-year-old has scored seven goals in nine appearances in all competitions, including six in seven league games.
Real visit Atletico for the Madrid derby on Sunday evening.
