Villarreal manager Marcelino claims the refereeing was "not equal" as his side were eliminated from the Europa League after a 3-0 defeat to Liverpool.
Marcelino claimed referee Viktor Kassai favoured the home side, who went through 3-1 on aggregate, after Victor Ruiz was sent off for a second booking with the score at 2-0.
Jurgen Klopp was involved in a touchline row with opposite number Marcelino in the first half after complaining about the ferocity of some of the visitors' tackling, but Marcelino had his own complaints.
"In the context of this game the referee was letting a lot go so to then see a sending-off you make your own conclusions," he said.
"I don't think the refereeing was quite equal for both sides."
The Spaniard admits the defeat was hard to take, but conceded that Liverpool were the better side at Anfield throughout.
He added: "Things didn't work out how we had planned them. It hit us hard conceding that early goal, it was a hammer blow.
"It was tough against an opponent who played with a huge amount of intensity, maybe on the margins of the rules at times but it was allowed.
"Liverpool played better than us but for all their superiority they didn't create too many chances.
"When we got to the sending off it was pretty much game over by then."