NORTH Melbourne's lofty reputation for avoiding injuries will be tested from next season after the sudden departure of two key fitness staff.

The Kangaroos today revealed Peter Mulkearns, their director of sports science and conditioning, and Ray Breed, their high performance manager, had both quit the club. It is believed Breed's first full season at the club was 2008, while Mulkearns was recruited from St Kilda in November 2009.

Despite the recent upheaval of AFL club fitness departments, it is not believed Mulkearns and Breed have been poached by a rival club.

North said the split with Mulkearns stemmed from a dispute over terms of a new contract that could not be resolved despite extensive negotiations.

"Peter has a long history with North Melbourne, is highly respected in the industry and has premiership experience but we understand his position," chief of football Donald McDonald said in a statement today.

Breed, meanwhile, was praised for playing a "vital" role between the clubs coaches, players and fitness staff.

"It's terribly disappointing to be losing people of Peter and Ray's experience and value at this time but we wish them all the best for the future," McDonald said.

Despite the departures, North's highly rated director of medical services, Steve Saunders, remains at the club.