John McEnroe, during his hey days, was known chiefly for being THE spoilt brat on the tennis court, the one who would give no quarter and expect everything, absolutely every single call in the match to go in his favour.
So, McEnroe never was about the sweet and kind when it came to winning tennis matches, and while the greats of the game might do it in their own way, that is true about anyone that has won multiple Grand Slams – when it comes to time on court, there can be no mercy.
Just look at the way Roger Federer dismantles his opponents when he gets into that zone, and you will know the true meaning of ruthlessness on the court.
One of the men currently failing to find that ruthlessness, which made him into the best tennis player in the world and one of the greatest of all-time, is Novak Djokovic, whose form has dipped, dipped and then dipped some more since winning the French Open title to complete a career Grand Slam last year.
Djokovic has been a shadow's shadow of himself for over a year now – relatively speaking, of course, because for a mere mortal, his record this year is still pretty great – with changes to his coaching staff also doing little to bring about a change in fortunes.
When he hired Andre Agassi, it was expected to bring an immediate shift to his form, turn him back into that winning machine, who ran through every single player on the circuit with ease. However, even Agassi could not inspire a title defence from the Serbian, who was knocked out in the quarterfinals at Roland Garros by Dominic Thiem, with the former world number one basically giving up in that final set, which was won by the Austrian to love.
Federer and Rafael Nadal have already shown the golden era of tennis is not quite over, there is still plenty left in the tank. But, with Djokovic now set to become a father for a second time – his wife is expected to give birth in August-September – is that desire, so crucial to get that ruthlessness on the court, even there for the 12-time major winner?
McEnroe feels the fact that Djokovic is now working with a spiritual adviser in Pepe Imaz is leaving him without the edge, the "killer instinct."
"From an emotional standpoint he perhaps felt he wanted to bring in somebody who wants to give people a lot of hugs," McEnroe said of Imaz who is known for his long hugs. "That does not necessarily translate to having that killer instinct.
"It does not automatically lose it, but you don't want to get into a situation where it is all peace and love and then have to go out and try to stomp on somebody's head in competition."
Djokovic has clearly lost the mental strength that made him near unbeatable at times. Look back during his insanely-good run, and you will find multiple times when he dug himself out of a hole the size of the Grand Canyon, purely through of that mental strength and belief in his ability.
Now, when Djokovic goes down a break or two or a set, he just seems to give in, much like he did against Thiem, something which would have been almost impossible to fathom 12 months ago.
Even that joy, he used to emit whenever he stepped onto the court seems to have dimmed a little. Have his priorities changed, and is there a serious basis to the rumours that have said the great man might just be ready to retire?
Maybe what Djokovic needs is a little break to re-evaluate his priorities and find that sweet spot of his again. It worked for Federer and Nadal, although those were injury enforced, and maybe, after Wimbledon and the US Open is done, the Serb can get away from the game, take a nice break and return as the Djokovic we all know.
Who knows, even before that, maybe the Agassi partnership will start to work like a charm, and Djokovic will be the one standing proudly on Centre Court with that famous golden trophy in his hands again in about three weeks' time.
The way things stand, though, that looks extremely unlikely.