Will Nick Kyrgios leave tennis regretting how much more he could have achieved? That is the suspicion of John McEnroe, another enfant terrible of the game, though never such a serial waster of talent as Kyrgios himself.

Recent concerns about Kyrgios’s state of mind were only amplified after he became involved in arguments with two different umpires at Queen’s Club on Thursday, earning code violations from each of them, before eventually flinging his racket off the court and instructing his critics in the crowd to perform an unprintable act.

The Association of Tennis Professionals fined Kyrgios a total of $17,500 for three instances of unsportsmanlike conduct on Friday, which will put a significant dent in his €28,620 prize money. But the broader picture is that he seems to have reached a point where any dubious line call throws him into an uncontrollable rage.

Admittedly, McEnroe might have called Wimbledon “the pits of the world” for the same reason in 1981, during his first-round match against Tom Gullikson. But he still went on to lift the title two weeks later.

Asked whether Kyrgios might look back at missed opportunities, McEnroe replied “We all think about that. No matter how well you do. You probably think about ‘What could I have done?’ Myself included. It would be hard to believe he wouldn’t think [that].