Dominic Solanke and Justin Kluivert struck the goals for the hosts.
Iraola said: "We had a lot of very good, clear chances. Sometimes Onana saved them, sometimes we did not have the finishes. We could not score more goals. We did a good game, played well.
Advertisement
Advertisement
"United always finds a way to be dangerous and score goals and when you don't finish these kinds of teams they find a way to score and get back into the game.
"We played very well today, I am very happy with the performance. We were the best team today. We probably have to find a way to win these types of games.
"We are in the right direction, we want to improve and finish the season strong. We have a difficult schedule ahead of us, a lot of games away from home against top teams but if we perform the way we did today we will have chances."