Blues boss Enzo Maresca made wholesale changes to the team which swept Nottingham Forest aside at the weekend, but their visitors were truly dreadful, and Ajax's job was made even harder after 17 minutes when Kenneth Taylor was shown a red card for a shocking challenge on Facundo Buonanotte.
The hosts immediately took advantage as Marc Guiu slotted home from close range, and they doubled their lead nine minutes later as Moises Caicedo fired home a deflected shot from outside the box.
There was a brief moment of hope for the visitors after former Manchester United forward Wout Weghorst smashed the ball home from the penalty spot after Tosin Adarabioyo fouled Raul Moro, but that was short-lived as Weghorst's clumsy challenge on Enzo Fernandez saw referee Felix Zwayer point to the spot, and the Argentina international finished with a fierce drive past Ajax keeper Remko Pasveer.
On the stroke of half-time, there was another penalty to Chelsea after Youri Baas fouled Estevao Willian, who was handed the ball by regular spot-kick taker Fernadez and duly dispatched his strike high to the keeper’s right. Maresca rang the changes at half-time, and it was another of the Blues’ youngster’s who extended the lead as Tyrique George made it five with a shot from range which took a massive deflection on the way past the helpless Pasveer.
GOAL rates Chelsea's players from Stamford Bridge...






