John Quinn's serious illness, ultimately diagnosed but for much of last year a mystery that baffled those around him, has continued to cast a shadow over the competition's youngest club.

Quinn is the man credited with re-designing the physical performance of the Essendon list when it last dominated the AFL competition and is the founding high-performance boss at Greater Western Sydney.

Unable to work at the Giants since last season, he has been diagnosed with a rare form of encephalitis.

The human condition is not only the highest priority facing coaches and fitness instructors at AFL clubs, but a source of heavily funded and highly competitive micromanagement. So it was a source of some confusion, trauma and ultimately sorrow among the Giants players and staff when the primary physical carer of so many young men began to show signs of personal fragility.

Quinn's behaviour, which so worried his colleagues and eventually was defined as a lymphatic form of a debilitating viral disease, landed him in hospital for the past four months and in and out of treatment before then. He is next week due to be released and is expected to move to Canberra, where he will live with family.

Still listed as the Giants' head of high performance, Quinn was recontracted in 2013 on a new three-year deal so highly was he rated by the club whose medical and performance team he largely recruited.

Quinn has not been replaced, but the club has hired extra staff to cover the significant gap left by his absence.

It is an absence that has personally affected the club's staff and one that has lingered since Quinn's initially undiagnosed struggles were first noticed by those who worked around him. In the days that followed the Giants' biggest victory and unforeseen upset win against Sydney, the human toll of establishment and credibility was lost on no one at the club.

While surgeons worked to save the damaged kidney of co-captain Phil Davis, it was Quinn's less dramatic but ultimately more poignant human story that continued quietly to occupy the club as it unfolded in another Sydney hospital wing.

Among his regular visitors have been his young family and his fellow GWS staffers, led by Graeme Allan. Kevin Sheedy called in last week and the pair spent some time reminiscing about their glorious year at Windy Hill in 2000 when the Bombers were regarded as one of the most formidable outfits in the game's history.

While the illness has affected his short-term memory, less recent events return more easily to him. Quinn came to Essendon from Australian athletics and was credited with working successfully alongside then captain James Hird, who became a close friend as he struggled with and ultimately overcame his navicular injury. Quinn's contribution at the Bombers also saw him house the problematic Andrew Lovett for several years.

The last time we spoke, the former Olympics coach was unhappy, like so many in his industry, at the bad name a few rogue performers were giving high-performance coaches and sports science in general.

Quite apart from Quinn's personal struggle is the financial impact his inability to work could have upon club, individual and family.

All three stories are completely different but the similarities in the stories of Quinn, Neale Daniher and the late Dean Bailey is that in each case the clubs concerned have remained loyal in every sense.

AFL boss Andrew Demetriou said he had been briefed on Quinn's condition and said the club would continue to support him. More generally, said Demetriou, all clubs tended to provide ongoing support in such cases and tended to ultimately settle with staff well beyond contractual requirements.

It is believed that Quinn has income protection, something AFL Coaches Association boss Danny Frawley has recently urged his members to consider. Frawley said several senior coaches had chosen to go down the less-costly insurance path of trauma protection.

Quinn's story continues, but now that he is unlikely to return to the Giants in an ongoing sense, it is worth pausing to consider his impact on the game and the less-heralded battle football clubs face every week, far removed from the events, between the first bounce and the final siren.