Manchester United midfielder Marouane Fellaini could face retrospective action for an act of violent conduct on Liverpool's Emre Can, according to former referee Howard Webb.
Fellaini appeared to lash out at Can late on in Liverpool's 2-0 victory over United in the teams' Europa League round-of-16 first leg at Anfield.
Webb, now working as a pundit for BT Sport, said Fellaini would have been sent off had Spanish referee Carlos Velasco Carballo and his assistants seen the incident and that UEFA could yet suspend the Belgian.
.@HowardMWebb expects UEFA to look into @Fellaini's off-the-ball "act of violent conduct" on Emre Can last night. https://t.co/dIeyNEFIZQ
- BT Sport Football (@btsportfootball) 11 March 2016
"To top off a bad night for Manchester United, they might face the second leg without Marouane Fellaini," former Premier League, Champions League and World Cup referee Webb said.
"At the very end of the game he had a word with Emre Can and ended up throwing a left arm in the face of Emre Can.
"If the referees had seen that it would have been a red card for sure and UEFA might want to have a little look at that as well.
"It's clearly an act of violent conduct. He's lucky that none of the six officials saw it on the day."
Liverpool boss Jurgen Klopp refused to be drawn on the incident after the match.
"There is nothing that I should say about the elbow but I saw it," Klopp told reporters. "I am not the referee -- you can write what you want but without anything from my side."