Real Madrid midfielder says Francisco "Isco" Alarcon has been diagnosed with appendicitis.
Madrid says tests on Tuesday showed Isco's condition requires emergency surgery.
Spanish media say Isco is expected to be sidelined for about a month. He could be back just in time for the clasico against Barcelona on Oct. 28 at Camp Nou Stadium.
He is also expected to miss Spain's friendly at Wales on Oct. 11 and the national team's match against England in the Nations League on Oct. 15.
