The US Open rules state that: ‘Players shall not at any time physically abuse any official, opponent, spectator or other person within the precincts of the tournament site.

‘In circumstances that are flagrant and particularly injurious to the success of a tournament, or are singularly egregious, a single violation of this section shall also constitute the major offence of “aggravated behaviour”.

‘For the purposes of this rule, physical abuse is the unauthorised touching of an official, opponent, spectator or other person.”.

Djokovic’s misfortune was Pablo Carreno Busta’s fortune.

The Spaniard qualified for the quarter-finals without having to sweat too much.

He joins Alexander Zverev, who destroyed Alejandro Davidovich Fokina 6-2 6-2 6-1 to book the first place in the quarters.