The Frenchman's choice is still being discussed. It was one of the main talking points leading into Saturday's pivotal clash between the two sides at Camp Nou.
Mundo Deportivo even labelled the encounter between the top two sides in the Primera Division as 'La Liga: The Decision'.
Barcelona held an eight-point advantage, meaning Atletico had to win to have any hope of overhauling their hosts before the end of the season.
However, while Griezmann was fully fit to start against the side he had so publicly snubbed, fellow forwards Diego Costa (hamstring) and Alvaro Morata (ankle) had only just returned to full training after injury issues.
That left Diego Simeone with his own difficult decision to make: leave both on the bench or select one to start in the hope of putting Barca's defence under pressure.
The Argentine ultimately opted to be bold, electing to start Costa. It proved the wrong decision. This proved a night for cool heads. Costa lost his. Lionel Messi and Luis Suarez kept theirs, and that proved the difference between the two sides.
For roughly 28 minutes, though, we had a game; more than that, we still had a title race. But then Costa did what Costa does, descending into a rage for no reason whatsoever to earn himself the most senseless of red cards for dissent.
Did Gil Manzano over-react to being verbally abused? Perhaps. But we don't know exactly what was said. What we do know is that Costa deserved to be punished for a ridiculous act of stupidity.
It was even difficult to know exactly what had so angered him. Arthur had gone to ground to win a ball in the middle of the park, and appeared to do so cleanly. Costa, though, was enraged and launched a verbal volley at Manzano.
The notoriously trigger-happy official immediately reached for his yellow but Costa continued his tirade, so Manzano brandished a red instead.
Atletico were incensed. Both centre-halves, Diego Godin and Jose Gimenez, were booked for protesting. They felt that the ref had wronged them. In truth, though, it was Costa who had let them down.
Unsurprisingly, the game changed completely with his exit. Even Barca appeared unsettled by the controversy, at least until half-time.
Before Costa's dismissal, the hosts had struck the post through Jordi Alba – after perfectly controlling an exquisite ball from Messi – and seen Philippe Coutinho draw a fine one-handed stop out of the brilliant Jan Oblak.
After the red, though, they did next to nothing for the remainder of the half. After the break, though, they gradually cranked up the pressure.
Predictably, Atleti responded admirably, spurred on by Simeone, who ended up replacing both full-backs, Santiago Arias and Filipe Luis, with two forwards, Angel Correa and Morata.
However, with just five minutes remaining, Suarez calmly picked up a pass from Jordi Alba and almost effortlessly bent the ball past a full-stretch Oblak with the aid of the right post.
With Atleti still reeling, Messi tore into the area just 90 seconds later, and despite being temporarily unbalanced by Gimenez, composed himself and then waited until the last possible second before almost nonchalantly sliding a shot into the same corner.
The wild celebrations that greeted both goals said it all: game over but, more importantly, title race over.
Barca now boast an 11-point lead with just seven rounds remaining. La Liga is effectively theirs. Again. It will be their eighth in the past 11 seasons.
Unfortunately, Atleti's season is now over, having already been eliminated from Europe after that dreadfully uncharacteristic collapse in Turin against Juventus.
They had missed the injured Costa on that occasion, slumping to a strangely passive defeat without their pugnacious No.19.
In that context, it's easy to understand why Simeone gambled on Costa's aggression to win them the game. Unfortunately, it was the reason they lost it.