By Duncan Johnstone

New Zealand heavyweight boxer Joseph Parker has a new opponent for next weekend's fight in Germany after Sherman Williams was caught in a contract dispute after being kicked out of Wladimir Klitschko's training camp.

Williams, the Bahamas veteran, was helping Klitschko prepare for his world title defence against Australian-Samoan Alex Leapai.

Williams was sparring with Klitschko but fell out of favour. Details are sketchy but he has now left Europe to return home and is refusing to fight Parker.

Klitschko's K2 management are demanding boxing authorities slap Williams with a six-month ban.

The result is Parker's promoters have had to find a last-minute opponent.

That comes in the form of Brazilian Marcelo Luiz Nascimento. They will clash on Klitschko's undercard on Saturday.

It's the third opponent lined up for Parker for this glamour date.

He had already adjusted his approach following the unavailability of undefeated Ukranian prospect Andriy Rudenko, Parker now faces more disruption. Having focused on the squat Williams, Parker now eyes the tallest opponent of his seven-fight professional career.

Parker and his trainer Kevin Barry face some last-minute adjustments as they round off their preparations in Essen, Germany, this week.

The hard-hitting 33-year-old Nascimento made a strong start to his pro career among Brazil's heavyweights, stopping his first 13 opponents.

That run booked him a date with undefeated British talent Tyson Fury at Wembley Arena in 2011. Fury emerged the victor, with the fifth round stoppage a candidate for knockout of the year as Nascimento succumbed to a monster right hand from the now 22-0 Brit.

Nascimento has had a difficult time since then, losing four of his subsequent eight fights, including a third round knockout loss to Australian Solomon Haumono in Melbourne last October.

His career now stands at 17 wins (15 kos) and five losses (3 kos) from 22 fights.

Parker's promoters, Duco Events, have taken a philosophical view to the late hiccup.

"Once it became clear that Sherman would not be fighting - and it became evident to us some time ago he was wavering about stepping into the ring with Joseph - finding the right opponent for Joseph became our priority," Duco's David Higgins said.

"Naturally we are disappointed because we truly believed Joseph would be the first person to stop the Tank in his tracks.

"But Nascimento represents just as big of a challenge. He's a huge guy with plenty of power. This is a dangerous fight, particularly given that Joseph has now twice had to adjust his game plan for a new opponent."

Added Duco's Dean Lonergan: "We're genuinely worried about this fight. It tests Joseph in a way we didn't want to test him. He's gone from fighting a short opponent to fighting the biggest man he's ever faced. Kevin Barry doesn't have much time to rework the fight plan after Sherman got scared and refused to fight."