It ended 0-0 at the Stadio Olimpico, the first stalemate in Serie A for Napoli after they had won eight out of eight this season.
Chances were at a premium, but the tension was sky high, especially on the benches.
Mourinho was already booked for dissent in the first half, then reacted with near hysteria to a potential foul not given to Nicolò Zaniolo.
This prompted an inevitable second yellow card and therefore a red for the Special One, who responded with a sarcastic thumbs up.
Spalletti, meanwhile, had a different battle going on with the Roma fans, who still blame him for forcing Francesco Totti into retirement.
As the ultras hurled abuse at him, the coach decided to respond with sarcasm by waving to them in thanks.
It perhaps was a bad sign, because at the final whistle Spalletti applauded referee Davide Massa for his control of the match.
Massa assumed it was sarcastic applause and sent Spalletti off for dissent, leaving the coach stunned.
Just have a look at José Mourinho 👀😂
Three days after a 6-1 defeat to Bodø/Glimt, the AS Roma boss is sent off! 🟥
A sarcastic thumbs up to the referee for good measure 👍
Oh, Jose… pic.twitter.com/iI0QPM68oy
— Football on BT Sport (@btsportfootball) October 24, 2021