Supporting critical posts of his substitution may have felt good at the time, but it won't go down well with those around him at Carrington today. And no, we're not just talking about his manager.
Although the headlines and fabricated claims of division are unwelcome for Ten Hag, the manager might be happy to see his young winger angry, upset and determined to prove him wrong.
Garnacho now knows that if his performance isn't up to scratch and he doesn't track back when required, he won't be staying on the pitch. It was a harsh lesson for the youngster and one that Ten Hag will be confident does the trick.
However, the main issue is the disrespect Garnacho has shown his teammates - particularly his replacement at half-time, Amad Diallo, and senior colleague, Marcus Rashford.
The two posts Garnacho liked from Mark Goldbridge of the United Stand, as much as they were directed at Ten Hag, the greater insult was for Amad and Rashford.
"Garnacho has been one of our best players this season," Goldbridge first posted, which was approved by Garnacho. "Poor first half but taking him off at half-time and holding him up as the problem is a joke. Many have done much worse week in week out and are still out there."
Then another, again with Garnacho's support, stated: "Ten Hag subtly blaming Garnacho in the post match press conference... not a good look throwing a 19-year-old under the bus who has actually delivered for you this season. But then again he's clearly scared of upsetting the bigger earners."
It's not unreasonable to suggest that both Rashford and Amad would be upset if they came across such claims on their social media feed. Amad was excellent in the second half and the idea that he should be forced to wait for his chance even when Garnacho is underperforming is harsh on the Ivorian.
And then you have Rashford. He wasn't at his best on Saturday, but again, Rashford seeing Garnacho approve a post suggesting Ten Hag is favouring him over his younger teammate isn't going to sit well.
Yes, you want Garnacho challenging Rashford for his place. Pushing him, pressuring him, but that's for the training pitch and on matchday. You don't disrespect teammates in public and on social media.
So lesson learned? You hope so. And you also hope Rashford and Amad, along with any other teammate who felt aggrieved by Garnacho's actions, don't let things linger.
Indeed, they shouldn't. Ten Hag certainly won't, even though the headlines suggest it should be he who feels the most insulted. The Dutchman knows young players, understands their temperaments and will be able to recognise that Garnacho was simply letting off steam.
