RUGBY league's showpiece World Cup is facing its first - but possibly not last - credibility test after Anthony Tupou was called into the Australian squad just hours after he trained with Tonga.

Tupou yesterday replaced Michael Crocker in the Australian squad after the Hull-bound forward was ruled out of the tournament with a rib injury. That meant that, effectively, Tupou was named in two squads within 24 hours.

The former Sydney Roosters forward - who will join Cronulla, the club of Australian coach Ricky Stuart, next season - trained with the Tongan squad at Henson Park yesterday morning, but by mid-afternoon, he was a Kangaroo again following Crocker's withdrawal after he damaged his rib during the Storm's NRL grand final loss to Manly last Sunday.

The injury has effectively ended the representative career of Crocker, and at the same time has eroded the credibility of the 10-team competition, due to begin on October 25.

Tournament director Colin Love yesterday defended the World Cup, saying: "There's a number of players with dual eligibility. Anthony Tupou played for Australia in the Anzac Test, but if players don't make the Australia or New Zealand team, they have the right to play for their second country, so to speak. Anthony wanted to play for Australia but he initially missed out on the Australian team."

While Tupou would have had to seek clearance by the Rugby League International Federation to play for Tonga, with Love saying he was "no guarantee" of receiving it, the fact the 25-year-old was named in a strong Tongan squad on Wednesday, then trained with his teammates the following day, will give a free-kick to critics of the tournament.

Had Tupou been granted permission to play for Tonga before Crocker was ruled out, he would clearly not have been allowed to switch allegiances again.

But Love maintained: "Anthony has not made any application to play for Tonga. Anthony had elected to play for Australia and you can only change that election once in a two-year period. He hadn't made any application. It doesn't just follow that the application will be granted."

The Tongan coach, former Parramatta and Bulldogs hardman Jim Dymock, said he was "disappointed" to lose Tupou but stopped short of criticising the tournament's eligibility rules.

"He's a quality player and he was at training [yesterday] morning - that's how keen he was," Dymock said. "We thought he was going to play for us, but it's not to be. Everyone wants to play for Australia. I know he was disappointed to be knocked back in the first place. It would be pretty hard to knock Australia back - he's been groomed in Australia.

"It's a bit hard for us to be dirty on them. It just makes it a bit harder - we haven't got as many high-quality players in our pool that we can pick from."

The ARL yesterday took the step of releasing a statement after Tupou's selection in the Australian squad, with chief executive Geoff Carr saying: "The only country Anthony is eligible to play for in the rugby league World Cup is Australia."

The Tongans are also bracing themselves to lose another quality NRL forward, Cronulla's Fraser Anderson, who had shoulder surgery last week.

But Tonga and Australia weren't alone in losing high-profile talent as the tournament was robbed of more star power. Also yesterday, New Zealand lost Melbourne prop Jeff Lima (knee) as well as Leeds fullback Brent Webb (back). They were replaced by Warriors front-rower Evarn Tuimavave and Dragons winger Jason Nightingale. And another Melbourne forward, prop Brett White, pulled out of Ireland's squad due to a toe injury.

Brisbane's Australian centre Justin Hodges had scans yesterday on an injured shoulder, raising the prospect of Parramatta's Jarryd Hayne being drafted from the Fijian squad into Australia's.

At least Crocker's injury spared the Australian officials of the prospect of tensions among teammates. The lead-up to the grand final featured talk of friction between Crocker and Manly's Test prop Josh Perry over a falling-out between the latter and former Storm player Clint Newton.