Atletico Madrid boss Diego Simeone has said that the capital side will miss the "very important" Koke while the Spaniard is on the sidelines.
The 23-year-old suffered a thigh injury in Saturday's 2-0 win at Eibar and is now expected to be out of action until the start of October.
Simeone is confident that he has the personnel to fill in for the Spaniard, but has admitted that the injury is a blow to the Madrid side.
"He's a very important player for us. He is very complete," Simeone told AS.
"He can pass between the lines, he's strong with set pieces, does a lot for the team and he interprets perfectly what we need from the midfield. But we are working well with other players, who are waiting for their chance."
Atletico return to La Liga action at home to Getafe on Tuesday evening.