Atletico won 2-0 in the first-leg of their quarterfinal thanks to goals from Julian Alvarez and Alexander Sorloth. Pau Cubarsi was sent off - via VAR - for Barca before Alvarez's opener.
However, there were complaints from Barca after VAR chose to ignore Atletico fullback Marc Pubill handling the ball inside the area. The defender grabbed the ball after a Musso goal-kick had been taken, believing the referee was calling for a restart. Both the match officials and VAR appeared to excuse Pubill's actions and the goal-kick was retaken.
Afterwards, Musso said of the incident: "If we're going to sum up the game based on that one play... Let's talk about the game in general. They played a very good match.
"They're a fantastic team, it's a pleasure to play against them, and they make us better. Pubill's play doesn't change anything. If Marc Pubill had wanted to take advantage because he was under pressure, it could be interpreted differently, but that's not the case.
"Let's stop kidding ourselves. It's a play that has no significance whatsoever. We're talking about absolutely nothing."
Atletico coach Diego Simeone also said: "Common sense, if Pubill was receiving a supposed pass to start the play, he interpreted it as he interpreted it, and the referee interpreted it the same way as Marc himself... It's common sense in the game, afterwards we can look for all the situations we want."