Sergio Aguero is growing disillusioned under Pep Guardiola, with his long-term future at Manchester City in the balance. The 29-year-old is frustrated at a lack of confidence shown in him for big games, similar worries he harboured last season. Sportsmail can reveal that chairman Khaldoon Al Mubarak met Aguero in Los Angeles during their pre-season tour to address the striker's concerns. Al Mubarak is understood to have told City's all-time leading goalscorer that the landscape with Guardiola would change this season. Aguero believes that has not been the case, however, and while he is delighted at City's form, holds doubts over his own position amid a strained relationship with Guardiola. He was an unused substitute for this month's derby victory at Old Trafford and let his annoyance be known when hooked early against Tottenham last weekend by throwing his gloves to the ground.