Villarreal manager Marcelino indicated that perhaps the officiating on Thursday night favoured home side Liverpool.
The Spanish side were beaten 3-0 by the Reds at Anfield in the Europa League semi-final second leg to have their run in the competition ended on Merseyside.
It is widely accepted that Liverpool dominated proceedings but Marcelino was of the belief that his side were harshly judged after Victor Ruiz was sent off for a second yellow card and Denis Suarez was denied a penalty when pushed by Alberto Moreno.
"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 of match official Viktor Kassai.
"I don't think the refereeing was quite equal for both sides."