Emi Martinez confronted the referee after his penalty decision decided the game as Aston Villa lost to Club Brugge.
It was their first defeat in the Champions League and ends their perfect record after they'd won their opening three games. The Belgians were not expected to be their toughest opponents but produced a shock to secure a narrow 1-0 win.
Brugge captain Hans Vanaken converted from 12 yards after a strange serious of events that saw Tyrone Mings pick up the ball when Martinez passed to him from a goal kick. The Villa centre-half clearly didn't realise the Argentine had restarted play and handled the ball.
VAR intervened to check but deemed that play had begun, meaning Mings was guilty of a handball. Martinez didn't see it that way and took issue with referee Tobias Stieler after the game - telling him to "watch it back" before he was dragged away.
Ezri Konsa came out and defended his team-mate, questioning why Mings wasn't sent-off if the referee felt it was a deliberate act given he was already on a yellow card.
He told TNT Sports: "I didn't see it, i just saw the players running to the ref saying 'handball.' It kills the game. If he's on a second yellow and it's deliberate, why not send him off? It is a mistake, but it's not a mistake we want to make, just got to move on from it."
Unai Emery was equally stunned to see the blunder - which he claims is a first for him. The Spaniard said: "It is completely strange this mistake. It's the biggest mistake we've made in my career as a coach. This mistake is very strange, but it is not for Tyrone Mings or Emi Martinez. It has only happened one time in all my life. Today."
Peter Crouch attempted to defend the England defender, suggesting that the usual routine will be for Mings to pass to Martinez before the team look to play.
He said: "I was just thinking, it is probably muscle memory, trying to stick up for Mings even though what he did was wrong. Emery's attention to detail they'll train this every day and it'll be Mings passing to Martinez every day."
Villa have now failed to win in four consecutive games in all competitions, which includes losses against Tottenham and Crystal Palace, and travel to face Premier League leaders Liverpool on Saturday.