Red Bull team boss Christian Horner said under-fire driver Sergio Perez had been in a “head-spin” in recent races and warned the Mexican that he needs to “realise his potential”.The 34-year-old Perez, who agreed a contract extension in May, was fourth in Friday practice for this weekend’s Hungarian Grand Prix.World champion and teammate Max Verstappen was second behind pace-setter Lando Norris in a McLaren.In his last six races, Perez has contributed only 15 points for Red Bull compared to Verstappen’s 119 while rival teams have improved and started winning.”We all want ‘Checo’ to realise…