This was a moment for Gunners boss to be strong - and he failed
Your star striker has a strop and takes you on. Do you:
A) Ignore it and pick him anyway because he is so important.
B) Drop him to show him that the team are bigger than one player.
C) Drop him - and then bring him on in desperation at half-time because your team are being battered in a big game.
Whatever the rights and wrongs of Arsene Wenger leaving out Alexis Sanchez last Saturday against Liverpool, the answer is definitely not C. It is never C. And Wenger should know that.
C is the position of weakness. C is what you do when you are not fully in control of the situation and are doing what you think is right rather than what you believe.
C sends out the wrong messages, making you look weak and without the courage of your convictions.
Contrast what Wenger did at Anfield with a similar scenario that reared its head for another club just a few weeks ago.
Again it involved the star striker who had a training-ground bust-up, over an injury this time, which then developed into a heated row with his manager. Again the player was dropped.
Except Diego Costa was left out completely by Chelsea manager Antonio Conte. He was not named among the substitutes and he did not travel to the game in January against Leicester City, even though Chelsea were desperate for a win to bounce back following a defeat by Tottenham.
And Chelsea did win, convincingly so. They beat Leicester 3-0, with Conte maintaining that Costa had been left out purely because of a back injury and not because he was unsettled and wanted to quit - although the manager chose his words so carefully that it was left open as to whether or not it was just about the striker not being fit enough. But, whatever, it felt like the team came first.
Leicester away for Chelsea and Liverpool away for Arsenal may be two different propositions, but Conte's line was clear and unequivocal.
And Costa's exile - or injury - lasted just the one game. He was soon back in the fold, back in that team and, of course, scored in the very next game, at home to Hull City in a 2-0 win. But the boundaries had been set for him and the rest of the Chelsea players.
It has been said that dropping Sanchez is Wenger's Ruud Gullit moment, an echo of the then-Newcastle manager's decision to leave Alan Shearer on the bench in the Tyne-Wear derby in 1999. Newcastle ended up losing the match and Gullit resigned as manager three days later.
A more up-to-date comparison, and one that resonates, is that this was Wenger's Conte moment. And he failed it.
Sanchez is no Alan Shearer, who was simply desperate for Newcastle to be better. Sanchez wants that but he also wants what is best for him. No one can blame Sanchez for being frustrated with this Arsenal team and, by extension, Wenger, although there are more productive ways of showing it.
But there also has to be more of that combustibility at a club where it has been too cosy for too long.
The strongest dressing-rooms have a bit of conflict and tension and a sense of self-policing, of sorting it out between themselves and delivering a few home truths. Professional football is not about being nice or anodyne.
If, as seems to be the case, Sanchez wants out of Arsenal - with Paris St-Germain his most likely suitor - then fair enough. Let him go.
Wenger appears to have grown tired of Sanchez's behaviour, and there is a mood around Arsenal that the Chilean has been playing for himself for some time, with a questionable work-rate and attitude making him harder to manage.
Dropping Sanchez is Wenger's prerogative. The problem is that last Saturday he did not really drop him. Or send him to train on his own. Or deliver an ultimatum that he is only back in the side again if his attitude improves.
Instead, he was kept on the bench until the match turned against Arsenal - a half-and-half solution, a milky response that left the manager appearing weaker, not stronger.
And Wenger needs to appear stronger, because all he has done is feed the narrative that he and his club are lost in a fog of uncertainty.
There is less than three months of the season to go and we do not know whether Wenger is staying; that two-year contract extension remains unsigned, and it all appears to come down to what happens next.
Neither do we know if Sanchez or Mesut Ozil - Arsenal's biggest-name players, each with a year left on their contracts - are staying. The players do not know what Arsenal are asking them to sign up to.
It has led to a self-perpetuating, enveloping fog. It has led to uncertainty and speculation. A power vacuum.
It means Arsenal, and Wenger, appear stuck in a limbo that has become almost paralysing.
It means that Sanchez is dropped but only half-dropped, a move that lacked the decisiveness, the clarity of thought and action, shown by Conte at Chelsea.
Wenger must already be regretting it.