Manchester City manager Pep Guardiola says his side are "in trouble" with a mounting injury list that threatens to disrupt the club's perfect start to the season.City only had six outfield players on their bench for the 3-1 Champions League victory over Red Star Belgrade.And their seventh successive triumph in all competitions came at a cost as midfielder Bernardo Silva became the latest player to pick up an injury which, according to Guardiola, will keep him out for "the next few weeks".The Portuguese international joins Kevin de Bruyne, Jack Grealish, Mateo Kovacic and John Stones on the sidelines.