"But getting closer to the fight I'm leaning towards Klitschko now. I want Joshua to win. It will be exciting for boxing and if I get past Razvan I will get the opportunity to fight those guys in the future, but I have a feeling that if Joshua doesn't knock him out early then Klitschko's experience will help him through.
"There's no doubt he [Joshua] has got power; [but] skill-wise and technique-wise, I still think Klitschko has it. I've seen him in camp, I've seen how he operates. He hasn't been the underdog for a long time. He's never been in the position where everyone is doubting him, where everyone thinks Joshua is going to walk over him."
Parker sparred six or seven rounds with Klitschko in Florida three years ago, an experience which taught him a great deal about himself and also the veteran Ukrainian. It is said that Parker did well against Klitschko in the ring, although the Kiwi would only say he believes he earned the Klitschko camp's respect.
"I'm not sure if he can pull the trigger the same. After the [Tyson] Fury fight everyone thought 'no, Klitschko is finished now'. But if he can pull the trigger the same and be the Klitschko who dominated for a long time I think he will come out on top."
Joshua's main weapon is his power and in particular the power of his right hand.
Asked how difficult it was to land power punches on Klitschko when they sparred, Parker said: "He's developed this defensive style so it is quite hard to get in there and throw your punches at him. But then again that was in 2014, at the beginning of our camp, and my fitness wasn't the best. I think if I was fitter and sparred with him now with the skills I have developed over the years I would do a lot better.
"That time I did quite well and they were pleased with the work that we gave. I think we gained their respect."
There is no doubt that Joshua has never faced anyone of the class of Klitschko, and that while he has the power to stop his opponent, he has also shown a vulnerability in defence at times.
Apart from that, most fighters who get in the ring against him don't believe they can win. Klitschko is supremely confident he will.
"With a guy like Klitschko you need to work on angles and speed," Parker said. "You need to give him a lot of head movement. Tyson Fury is the perfect example - dancing around with that awkward style.
Asked about the atmosphere in the arena, Parker said: "I can't even imagine it. I worked out to 10,000 for the fight with [Andy] Ruiz. I think the atmosphere will be crazy. The UK fans love their boxers and athletes so I think when Joshua walks out it will be deafening."