Ronald Koeman had a spat with the Juventus bench as Barcelona were thrashed 3-0 at the Nou Camp.
Los Cules were already through to the next round but it is another result that puts pressure on the Dutch manager.
Despite arriving in the summer, the ex-Netherlands boss has had an uneasy start to life as Barcelona's coach.
They were humbled at the weekend by newly-promoted Cadiz to leave them ninth in La Liga.
Barca's European form had been their redeeming light with five wins out of five until Tuesday night.
Cristiano Ronaldo was making his first appearance at the Nou Camp since his move to Juventus in 2018.
And he ended up being the main man, outshining Lionel Messi who was largely anonymous compared to his old rival.
The Portugal international scored twice from the spot with Weston McKennie also getting in on the act.
While there were fireworks on the pitch, there was some flames off of it too.
Barca boss Koeman became incensed with the Juve bench, who were demanding that Clement Lenglet be sent off.
According to Football Italia, the former Everton manager fumed at Juventus' players - telling them to "shut up".
The incident occurred after the Frenchman was found at fault by VAR to have committed handball in the box.
It allowed Ronaldo to net his second spot-kick but that was not enough for some members of Juve's players.
Lenglet was already on a booking and there were question marks over whether a second yellow was forthcoming.
Juve's players on the bench demanded he be sent off which Koeman took offence to.
As he fumed, Football Italia further report that the Serie A club's subs were laughing at the Barcelona manager.
Remarkably, Ronaldo's brace took him to 14 goals at the Nou Camp - more than any other away ground.
It also took him past an astonishing 650 club goals in his career.
Additionally, the ex-Real Madrid star became the first player in Champions League history to convert twice from the spot at Barcelona's stadium.
