Chelsea midfielder Eden Hazard was sent off for kicking a ball boy during the Capital One Cup exit to Swansea.
The Belgian was trying to retrieve the ball from under the ball boy who had fallen on top of it. The ball boy had failed to return the ball promptly after it had gone out for a goal kick.
Referee Chris Foy showed the 22-year-old a straight red card on 80 minutes.
Blues boss Rafael Benitez said player and ball boy apologised to each other after the match at Liberty Stadium.
"The boy was apologising for time wasting. Hazard was frustrated and tried to get the ball. He was kicking the ball and getting the ball.
He added: "They both recognise there was a mistake.
"We can analyse if for half an hour but we know that both are wrong."
Swansea captain Ashley Williams said: "Demba Ba told me that the boy held on to it. I saw him [Hazard] kick him in the ribs, and you can't do that."
Swansea manager Michael Laudrup commented: "I think he [Hazard] will regret it when he sees it. The ball boy should have let it go but he was pushed first and then he kicks him.
"I understand as a player when you are behind and you are under pressure you sometimes say or do things you shouldn't but there are some things you cannot do."
Chelsea drew the match 0-0, with Swansea progressing to the final with a 2-0 win on aggregate.
Former Premier League referee Dermot Gallagher told BBC Radio 5 live: "There was a precedent when Liverpool defender Jamie Carragher was sent off for throwing a coin into the crowd against Arsenal at Highbury in 2002.
"Referee Chris Foy was absolutely correct to send off Eden Hazard, it is violent conduct. He has quite rightly sent him off. He will report it as an act of violent conduct to the FA."