Manchester United boss Erik ten Hag cancelled a planned day off on Sunday after the 4-0 humiliation at Brentford.
With no game until the visit of Liverpool to Old Trafford on 22 August, Ten Hag had intended to let his squad have the rest of the weekend off.
However, the manner of Saturday's loss prompted him to revise his plans.
It is understood he was at his desk at Carrington early on Sunday to rake over the coals of a catastrophic defeat that has drawn criticism from all quarters.
The loss prompted a sparky debate on Sky between Jamie Redknapp and former United skipper Gary Neville, who called for the club's owners to offer an unprecedented public explanation for what is going wrong.