WBO heavyweight world champion Joseph Parker believes Anthony Joshua's muscular physique will be working against him when a unification comes together.

Their respective promoters are in talks for a showdown in early 2018.  Two sides were very far apart on the money two weeks, but things appear to be coming together as their teams are inching closer to being on the same page when it comes to the financial terms.

Joshua' s promoter Eddie Hearn has mentioned a date falling down in March or April - and possibly at the O2 Arena in London.

Parker believes that Joshua's muscles are going to be an issue for him when it comes to stamina and fighting in a robotic manner.

"He looks great but I think it can be a bit of an issue with his stamina and being a little bit robotic. Look at some of the greats of the past like Ali, he was never ripped up," Parker told Fairfax Media.

Parker himself was gaining more mass to improve his ability to deal with bigger heavyweights, but noticed quickly that his speed was affected and his stamina. When his trainer Kevin Barry noticed those problems, he made his boxer cut down the excess weight. 

"I can get to a point where I get pretty chiselled. It comes down to diet but there's also the body type ... my Pacific Island genes will never allow me to be the most ripped but I think I can get pretty close to it," Parker said.

"The work I've been doing with [personal trainer] Sean [Hughes] has been very beneficial. I see a lot of positives from it. I see that it's helping with strengthening the smaller muscles. It is going to be awesome to see the difference it makes when I go to my next training camp and get into sparring. I think it will improve everything ... footwork, speed, agility. I'm really looking forward to testing it in full camp."

Joshua, who holds the IBF, IBO, WBA world titles, was in action last month when he stopped Carlos Takam in the tenth round in Cardiff.