Manchester City boss Pep Guardiola admits they'll miss John Stones.
Stones broke down during their Champions League win against Young Boys last season, with Guardiola later confirming a "muscular injury".
Guardiola said, "I feel so sorry for him.
"He is so important for what he does."
Asked if he expects Stones to be kept out for a while, City's Spanish boss added: "I think so. [It is a] muscular injury, it will be a while. It is a pity, it is bad news for us. I don't know how long."