Atletico Madrid midfielder Koke faces three weeks out with a hamstring injury.
Koke broke down during the derby thumping of Real Madrid.
A statement from Atletico read: "Koke has undergone test on Monday afternoon after getting hurt in the opening stages of Saturday's derby.
"The results have confirmed a Grade II muscular lesion in his right thigh.
"The Spain international will begin treatment and he will continue to be evaluated."
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