While they will host Palace on the back of victory at Manchester United, Iraola insists the Eagles are finding their best form.
“Probably they started slow and now they've been growing during the season and probably we are going to face them where they are in the better place they've been,” Iraola told the Daily Echo.
“It's true that they come from two games against Arsenal that, even playing well and being ahead and having their chances, it’s always very difficult against Arsenal and for sure for them, it's also an important game and I expect a level game and we have to be very good."
On Palace's attack, Iraola also stated: “They are going to be a threat.
“The five players they put up front, the wing backs, Daniel Munoz, Mitchell, Ismaila Sarr, Eberechi Eze, Mateta, Nketia, Kamada, they are top level players, very difficult duels to win.
“So, we'll have to be very good.
“But this is the Premier League. It doesn't change; we will play Palace and then we'll go to Fulham and they will have a lot of quality and we have to be at this level.
“There are difficulties in the Premier League if you are a fullback, you are a centre back, you will not have an easy game and we have to take it like this, try to help each other, especially the defenders.
“I think we are now in a good moment and I want to see them face the players you said like it happened yesterday to finish in a good spot defensively and I hope we can do it again.”