England number eight Nick Easter believes the staging of the Tri-Nations will given northern hemisphere teams an advantage at the World Cup.
New Zealand, Australia and South Africa will play each other in the annual tournament beginning on July 23. Even in its reduced format, adjusted to account for the World Cup, they will still play four matches that Easter claims could leave them "overcooked".
"This time the northern hemisphere teams might have a little bit of an advantage over the southern hemisphere teams in terms of the scheduling because we've had a break," said Easter.
"We don't have any rugby match now until the first warm-up game in August, so we have a good window to train hard and get prepared properly. But in the southern hemisphere their Super 15 season is longer than usual and has gone on an extra month. Then they have the Tri-Nations.
"They might be a little over-cooked, while for us it's just like heading into a normal season. At our clubs we'd be doing pre-season at this time and start playing in September."
The All Blacks and Wallabies have also arranged fixtures against Fiji and Samoa respectively as curtain raisers to the Tri-Nations.
It is a gruelling schedule that will require careful use of playing resources with the need to protect top players competing against the benefit to confidence levels of winning games against top opposition.
Of the RBS 6 Nations teams, only Ireland have a similar itinerary with five warm-up games and Easter suspects the contrasting schedules could make a difference.
"I am surprised they're playing the Tri-Nations. Maybe they'll play weakened sides and rest their key players," Easter said.
"I thought they might play each other as warm up games like we do with other Six Nations teams, but with the same sort of warm up schedule. I hope it leaves them tired."