A lethargic Chelsea side succumbed to four second-half goals as the Blues kick-start their 2015/16 campaign with a whimper.
Loic Remy put the hosts in front but, after 11 changes were made at half-time, including the introduction of new signing Asmir Begovic, the Bosnian and his team-mates went on to lose in dismal fashion.
It means the London side face an uphill battle in this three-match North America edition of the International Champions Cup, with PSG and Barcelona awaiting in the coming days.
Despite the loss, it would prove to be a good work-out for Mourinho’s men. Remy striked well from an Oscar assist, as the front three of Traore, Remy and Moses impressed.
All change at half-time saw New York Red Bulls an equaliser. Begovic’s desire to keep a debut clean sheet only lasted five minutes as Castellanos levelled.
Adams headed home to nudge the Americans in front, before Davis gave them breathing space. Hazard’s strike, from another Oscar assist, would have kept the intensity of the game going to the very end, were it not for another Davis goal which this time gave them daylight.