The young defender was signed last summer from Juventus, having spent the second-half of the season on-loan with AS Roma.
Huijsen is being linked with Real Madrid and Barcelona ahead of the summer market.
And Iraola said, “I think you have the feeling in the first trainings.
“You feel the player, you see the qualities straight away.
“I didn't know about his mentality because when you sign someone that is 19, you see, okay, it looks like he’s going to be a good player.
“But you are not sure if he's ready to perform straight away against the best opposition. That is what he's facing in the Premier League.
“And he showed since the first day, I think he started playing the season against Forest. He played really well.
“Straight away, once he got a good run of games, everyone sees now that he's a very good centre back.”
On Huijsen's qualities, Iraola said: “I think his mentality, his head.
“I think he's confident. He is not afraid of marking any forward and I think he's calm on the ball.
“He knows what he's doing, he's under control. Sometimes he will make mistakes like all the others, but there is always a reason for the things he does.
“And for someone that is 19, it's really strange to find this at this level.”