Joseph Parker has thrown shade on rival Anthony Joshua, suggesting the Brit may be using performance-enhancing drugs.
The two heavyweight kingpins are set for a unification fight on April 1 (NZT) in Cardiff that will see the winner walk out with three of boxing's four major titles.
Speaking to NZME, Parker mocked Joshua's appearance on The Graham Norton Show, where the pair described the Kiwi as "The Pie King" in reference to his physique.
Parker questioned if Joshua obtained his own impressive build legally.
''They call me the king of pies, but I call him the king of steroids," Parker told the Radio Sport Breakfast. "Who knows, if you are that big and that muscly, there's something wrong.
''I have heard word, I have looked at him and I have seen. He has been very close with Klitschko... he has been a reigning champion for a long time.
"So I don't know... it may be true maybe not."
Parker didn't go as far as labelling the IBF and WBA champion a drugs cheat, suggesting that the public can make their own minds up.
''I don't know how he will respond... he may be angry or upset at what we have been saying.
"It's part of the game. I am not accusing him of using steroids, but I am saying it is a possibility.''
"There are a lot of ways you can dodge drug testing."
Parker was full of bravado at the fight announcement, proclaiming that he will shock the world when the two giants clash at the Principality Stadium.
"Anthony Joshua is in for a huge shock," Parker said. "A couple of months ago, I heard him say: 'Why should I be worried about this little kid from New Zealand?'
"Well, now he's about to find out and the world is about to find out whether AJ can really take a punch.
"I am a relaxed, calm person. I have respect for Joshua - you do not have a 20-0 record, if you are not that good.
"But I think I can beat anyone in the world - I would not be here, if I did not believe in myself."
Both heavyweights are unbeaten in their careers - Joshua achieving 20 knockouts in 20 fights, while Parker's 24-0 record has come with 18 wins via stoppage.