It's funny how narratives and perceptions work in football...

Fred made ONE very innocuous foul all game.
He should have been sent off, but wasn't, and was perfectly behaved after that.
He was sent off for a perfectly fair challenge.

People are reacting as if you should ALWAYS take off a player who is on a yellow. I have never heard this narrative said for any other manager..

We don't have anyone on the bench who does Fred's job, so anyone who is saying that it's a simple choice to sub him, it isn't.

Bring Matic on, and we end up not pressing the ball as much, sitting back, inviting pressure.
Bring on VDB and the defence is more exposed. Midfield had already struggled to contain Neymar and Mbappe running through.
Same for Pogba.