She had lost the first set. Then she was penalised for being coached. An athlete in control of their emotions would have let it go, accepted the setback and got on with it.
But Williams could see that Naomi Osaka was playing the match of her life. Williams was losing and that wasn't in the script.
Cue the outrage. Let's see if my meltdown will put off my opponent.
It didn't work, thankfully.
The more she went on, the more any sympathy for her dissipated.
But we know she has form, and not only at Flushing Meadows.
Remember her solitary appearance in Auckland? Losing in the second round at the start of last year and then blaming the wind in what was one of the most ungracious media appearances you're ever likely to see or read about.
Yes, she is the greatest woman tennis player of all time. Yes, she is still – after 20 years – the greatest attraction in the sport.
But with that status comes a responsibility.
A responsibility to be at least a half gracious human being.
The incident which started Williams off does bring into focus a serious question which covers all sport – should there be coaching and/or advice given during a match?
In team sports it is part of the way things are done. American sports make an art form of it and commercial breaks are scheduled so basketball or football coaches can plan the next move.
The British sports are a bit more subtle. The football coaches have their lines on the side of the pitch from where they can shout instructions. Rugby coaches sit high in the stand and radio instructions down to the water boys. Cricket mentors have ample opportunity to impart their suggestions.
Most individual sports allow it too. You've seen the cycling coaches on the inside of the track calling splits and the athletics coaches proffering advice from the stands to the likes of Eliza McCartney or Tom Walsh.
The two sports which expressly forbid it are golf and tennis. Although that's not strictly true because in team events like the Davis and Ryder Cups the non–playing captains are giving their players as much advice as a Steve Hansen or Jose Mourinho.
The Rules of Golf (Rule 8 to be precise) expressly forbid a player receiving information from anyone apart from the caddy or playing partner and their caddy.
That's why when Tauranga's Jay Carter was coach with the New Zealand Eisenhower Trophy team in Ireland last week he would have observed from behind the ropes and did his work with the players afterwards.
Professional tennis has essentially the same rule. But unlike in golf, it seems to be breached all the time. That's why umpire Carlos Ramos, who's renowned as a stickler for rules, was right to call Williams for the actions of her coach in the stands.
But should golf and tennis do what every other sport does and just let it happen?
As long as the coach/manager/adviser is doing the job from outside the field of play, what's the problem?
