Wilder, who will put his WBC title against Gerald Washington on Sky Sports later this month, admits he is rooting for IBF champion Joshua, but believes he may fall short against 68-fight veteran Klitschko.
"My heart is for Joshua but my mind is always for Klitschko," Wilder told On The Ropes Boxing Radio. "We can't count Klitschko out. I don't think Joshua has had the well enough training or experience for Klitschko in my opinion. I'm not saying that Joshua would lose off that, but when you're fighting a certain type of calibre of fighters and then you move all the way up to the guy who at one point in time was the ruler of the division and held the belts for a long time, it's a big leap. We will see, maybe they got an idea or a plan that they are going to stand by, we'll see what happens. It's great that those guys are fighting, just to get the ball rolling."
Joshua and Wilder, who boasts a professional record of 37 wins, with all but one by knockout, both have previously shared sparring sessions with the 40-year-old Ukrainian.
"When I was in there with him, I just learned that he's very competitive," added Wilder. "If you come hard, he tries to come back harder. It's all about determining the will and who wants it the most when you're in the ring facing Klitschko. He still has loopholes in his game but we all do. When a fighter discovers certain weaknesses in a fight, he himself has to execute those loopholes, but if you can't do it, it's something that's just there. We all have different little holes in our game, we're going to see if Joshua can execute the things that he needs to do in Klitschko's territory. It's going to be a great fight and I'm looking forward to watching it.”