Essendon heavyweights Mark Thompson (senior assistant coach) and Dean Robinson (high performance manager) both worked at Geelong, with the former coach guiding the Cats to two premierships during their recent golden era that has claimed three flags in the past six seasons.
The Cats will be fearful that era could be tainted if the investigation finds Essendon guilty of doping.
Thompson left Geelong to work at Essendon in controversial circumstances, and brought Robinson (the Cats' rehabilitation and strength manager) to the Bombers.
Since turning up at Essendon, Thompson and Robinson worked hard to build up the bodies of the young Bombers, which has, arguably, been the cause of a spate of soft-tissue injuries that has dogged the club in the past two seasons.
After Tuesday's shock announcement, Geelong says it has nothing to hide and believes no one acted in "an improper manner" during their time at the club.
In a club statement, the Cats said: "The Geelong Football Club can confirm that an individual involved with the Essendon Football Club fitness program during the period currently under investigation was also previously employed by the Geelong Football Club.
"Whilst we have no evidence or information that this individual acted in an improper manner during his employment at the Geelong Football Club, we are ready to cooperate fully with the investigation."
The club would not comment further.
Meanwhile, Gold Coast also sent out a media release stating that one of its former staff members was involved in the controversy.
"In relation to the allegations today involving the Essendon Football Club, we confirm that certain individuals involved with the Essendon fitness program during the period under investigation briefly worked for the Gold Coast Football Club," the statement read.
"We have no evidence or information whatsoever that these individuals acted in an improper way during their time of employment with the Gold Coast Football Club.
"We stand ready to assist the AFL with any investigation it is undertaking in relation to this matter."
