The midfielder produced the kind of performance that had thousands of supporters calling for him to change his mind about leaving.
The 34-year-old opened the scoring with a header in the 11th minute and went on to make 11 tackles, win 16 duels and complete nine clearances — becoming the only player in 20 seasons of Premier League records to register all three totals in a single match.
At full time he walked from the pitch visibly overwhelmed, wiping tears from his eyes as the Old Trafford crowd gave him a standing ovation.
He later explained what the moment meant.
"I spent most of my career in Spain playing for Real Madrid, where I won many trophies. But in just a few seasons at Manchester United, I've felt something different — something deep enough to make a grown man cry.
"Here, I truly feel at home. At Real Madrid, winning trophies was incredible, but here at United, even a single victory feels just as significant — like lifting a trophy in its own right. That connection with the fans, that sense of belonging — it's powerful enough to move a grown man.
"And honestly, that's why I couldn't hold back my tears."
Michael Carrick was asked whether there was any prospect of a U-turn.
"It's pretty clear — from both sides it's pretty clear the decision. Credit to him because he's given absolutely everything and had some big moments for us, so all round it's quite a nice direction for it to be taken."
Casemiro will leave when his contract expires in June.