Jarrod Bowen scored a last-minute winner for West Ham as they go on to face Liverpool in the next round, however the ball seemed to hit his arm before he scored which led many to question the referee’s decision.
Iraola was outraged about the decision especially after their goal against Newcastle United last weekend was ruled out that would have won the game.
He spoke to the Daily Echo about the decision which cost his side.
“It has happened again. I think it's even more clear.
“I don't know what to say, really. I don't really know what to say. It's obvious that we are not making these mistakes.
“We are paying the consequences. This is very, very obvious. And we are out of the competition because a mistake of the referee.
“They score with the arm. It hits his arm and I don't know what we have to do to change something, but obviously it's costing us a lot.”
He spoke more about the handball and how clear it was in the replay.
“I've seen it in the video,” he said.
“From behind the goal, you see a camera, he wants to take the arm out.”
Iraola added: “If you see it, in 2 seconds (you will see the handball).
“I wasn't going to complain from the angle that I saw on the big screen here because it looked like arm ball.
“But I say I'm not 100% sure, I'm going to complain. But now they show me the one behind the goal and it's very, very clear.”