Hurricanes captain would like to see New Zealand derbies cut back to one per season.
Currently as the competition stands the New Zealand franchises play each other home and away throughout the season, but the quality of local opposition is taking its toll on the players.
"They're like Test matches, New Zealand teams want to kill each other," he said.
"I love playing the New Zealand teams, but I'm not being biased here - they are bloody tough."
There has been much debate around the tough schedule the New Zealand teams face in comparison to their Super Rugby counterparts from Australia, Japan, South Africa and Argentina, some of whom won't face New Zealand competition this season.
Coles believes that you have to be 100 percent focused on the task when faced with New Zealand opposition.
"You have to prepare very, very well against New Zealand sides - if you're 5 percent off you can lose to any of them. For me I would just like to see it at one a season," he explained.
"Personally, I love playing them - but once is enough."
The Hurricanes will guarantee playoff rugby by winning their last three matches and can go a long way to achieving that with victory over the Blues in Wellington tomorrow night.
Newshub.