The Cronulla flyer, who spent time at fullback in Australia's Tri-Nations trial on Saturday, believes the combination of a dominant forward pack, the presence of half Gareth Widdop and coach Wayne Bennett could cause Australia problems as they look to retain their World Cup crown.

A weakened New Zealand side are the punters' second pick while Tonga have firmed in the betting since Jason Taumalolo and Andrew Fifita joined them this month, but Holmes has warned his teammates of the threat posed from the northern hemisphere.

"It'll be pretty close with England I honestly think; they have a pretty strong team, they're usually pretty strong," Holmes said. "The forwards are very big, James Graham and the Burgess boys, they've got Widdop, a classy half there. When we played them over in England [at the Four Nations] they were obviously a bit tough and I felt like they were our strongest competitors over there and they do have some classy outside backs."

They've got [Elliott] Whitehead, a good back-rower there. They're pretty good all over the park and I personally think that's where we'll be challenged. They'll obviously thrive to play good for him [Bennett] and he seems to be doing well whatever team he coaches."

Holmes' theory gets an early test as Australia open their World Cup campaign against England in Melbourne on October 27. Should Australia top the pool as expected, the runner-up, likely England, will likely take on Papua New Guinea in the quarter-finals with the Kumuls expected to win their group.

Papua New Guinea beat Fiji 10-0 over 40 minutes in Suva on Saturday, while the PNG Hunters the Queensland Cup grand final last month in their fourth year contesting that competition. If England win a potential quarter-final, they'd be on track to clash with Australia in the World Cup decider in Brisbane on December 2. Billy Slater will play at fullback throughout the World Cup, shunting Holmes to the wing, where he'll likely stand outside future club teammate Josh Dugan on the right. Holmes played on the wing in last year's Four Nations and starred in that spot for Queensland in State of Origin this year, scoring three times in the deciding game.

The 22-year-old is expected to retain his spot as Cronulla fullback next season, despite Dugan joining the club."It would be good to start [a combination with Dugan] now," Holmes said.

"If I do play fullback or on the wing outside him, I'm sure he can create something for me and I can do the same for him.

"We haven't spoken about club-land at the moment. It's off-sesaon, we're playing for Australia now, we just have to worry about that

"I haven't mentioned anything to him. He's been playing centre for Dragons, he plays centre for Origin, he plays centre for Australia so it [not playing fullback at Cronulla] doesn't worry me.