Andy Ruiz is training very hard and appears to be in top form for his scheduled fight against Joseph Parker in Auckland next month - where the two heavyweights will battle for the World Boxing Organisation (WBO) title vacated by Tyson Fury.

The fight was officially announced last week for the Auckland's Vector Arena on December 10. Fury vacated last month in order to seek medical treatment after admitting he took cocaine to treat his battle with depression.

Parker, 24, who has a 21-0 record with 18 knockouts, is now the WBO's top-ranked heavyweight. Ruiz, 27, who is Mexican-born but based in the United States, has a 29-0 record with 19 knockouts.

This will be the first heavyweight title fight ever contested in New Zealand.

"This is a huge sporting event which I expect to unite the country," chief executive Martin Snedden said.

Ruiz is now training under the tutelage of veteran coach Abel Sanchez. With a new trainer, a new diet and training in Big Bear, California - Ruiz continues to drop the pounds every week.

And he's also getting a lot of help from Sanchez's most famous client, WBC/WBA/IBO/IBF middleweight champion Gennady 'GGG' Golovkin, who wants to see Ruiz topple Parker for the title.

"We're a team here helping each other. Every time GGG is here he makes me do extra stuff. He wants me to win and be world champion and he is a good guy. But I know that ultimately this is all up to me, aint no one going to train for me, or get in the ring for me. I have to get in the ring all by my own," Ruiz told Farifax Media.

Parker has some physical advantages - but Ruiz believes those advantages are going to become a nightmare for Parker.

"I have been fighting tall fighters all my life so this fight is not going to be any different," Ruiz said.

"I like fighting taller fighters because tall fighters don't like to fight short fighters  ...  they don't like them always being there. I like to move and always like being there, it gives problems to a lot of top fighters. I find short guys more difficult, they turn in a little ball and it's harder to get them. Taller fighters, with your speed and combinations, it's a direct target."