Arsenal's combative midfielder was given the marching yet again after his two-footed tackle slightly caught Cancelo close to the 18 yard box.
His sending off, the 11th in his career, was a summary of the gunners shambolic display and poor approach to the new season.
It took just seven minutes for Pep Guardiola’s men to register their first goal and stamp their authority with a header from Ilkay Gundogan.
The goal saw the early resistance by Arteta’s side crumbled as the Blues recorded four quick goals from Ferran Torres (2), Gabriel Jesus and Rodri.
Arsenal’s woes were compounded in the 35 minutes when Xhaka was sent off.
The Switzerland international was shown a straight red card for a reckless challenge after his studs-up lunge catches Cancelo slightly offguard.
Cancelo did well to move his leg out of the way of Xhaka’s two-footed lunge to avoid any serious injury.