Xabi Alonso says Real Madrid may need to "find solutions" after Trent Alexander-Arnold suffered a second muscle injury.
The right-back's Champions League debut for his new team lasted less than five minutes on Tuesday as a suspected hamstring injury saw him forced off against Marseille.
Alexander-Arnold pulled up and put his hand on the back of his left leg after an early sprint. He soon dropped to the ground to wait for medical assistance and was replaced by Dani Carvajal.
It is the second time in a matter of weeks that Alexander-Arnold has picked up a muscle complaint, having missed Madrid's Club World Cup exit to Paris Saint-Germain in July.
Madrid's task got even harder when Carvajal was sent off for headbutting Marseille goalkeeper Geronimo Rulli 18 minutes from time, but the Spanish giants went on to record a 2-1 victory thanks to two Kylian Mbappe penalties.
Asked for an update after the game, Alonso said he is waiting for clarity of the extent of any damage to Alexander-Arnold, but admits he could be left with a decision on his hands.
He told reporters: "We'll wait a bit; maybe it's not as bad as it seems.
"We have to be creative in finding solutions. [Raul] Asencio came in well. [Eduardo] Camavinga and Jude [Bellingham] are back and will be able to play on Saturday."
