Andy Ruiz Jr believes WBO heavyweight champion Joseph Parker will have to lift his game if he is to beat Anthony Joshua.
The 25-year-old Parker beat Ruiz by a majority decision to claim the vacant WBO world title in December 2016, but the Mexican-American Ruiz said Parker never pressured him much in the 12-round bout.
Now Parker's camp is eying up a Joshua's WBA 'super' and IBF belts in an attempt to unify the heavyweight division.
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Speaking to Boxing News, Ruiz believes Parker will have to do something special if he wants to hand Joshua his first career defeat.
"I think Joshua's a little too strong. Joseph didn't hurt me at all, not even one time," Ruiz told Boxing News.
"Joseph Parker's going to have to do something different to what he normally does to win this fight.
"But Joshua is pretty good. He stays tall too much. He never had a pressure fighter on him all the time. It would be a good match up.'
"I think it'll be a good matchup. It could go either way."
Parker's promoter David Higgins said earlier this week that talks had reached a deadlock between him and Joshua's promoter Eddie Hearn saying: "AJ is refusing to compromise and has drawn a line in the sand."
That made Parker send out another tweet directed at Joshua saying "65% and rematch not enough to unify? Believe your own hype? Bubble's gonna burst bro. #BigGlassRobot #NeverBeenDropped."
If both camps do agree to a fight, it is expected the bout will take place in March next year while Twickenham, Millennium Stadium or Wembley being touted as a possible venue.
Parker's trainer Kevin Barry told RadioLIVE that they have already begun preparing for the highly anticipated fight.