The 31-year-old was unable to feature for the Bombers last year after the complaint first appeared in the pre-season, curtailing his preparations for 2021 as an infection surfaced and soon required Hurley to seek further medical attention.
The Bombers defender spent a lengthy period in hospital and lost a reported 10 kilograms of weight as he looked to begin his recovery.
Essendon have been forced to take a conservative approach with the 193-gamer, with a timeline on his return remaining unclear.
Despite the journey ahead, Hurley is making "inroads" in his recovery as he enters his 14th year in a red sash.
“Particularly over the last six weeks he’s made some great inroads.
“I’m not sure when he’ll be back out on the track, but it’s great to see him knocking about.”
When asked whether Hurley will be fit for Essendon's Round 1 match against the Cats on March 19, Heppell revealed the two-time All-Australian won't be ready for his side's season opener.
“[That’s] probably a bit too soon in the way he’s progressing,” Heppell added.
“There’s no real time frame on it, honestly. He’s not putting any cap on himself, on when he can return, but it will come in due course.”
The Bombers made their return to training on Monday as they eye consecutive finals campaigns following their eighth-placed finish last year.
The 26-year-old is sure to add to a Bombers defence that showed plenty of poise and promise in Hurley's absence, with the likes of Jayden Laverde, Nick Hind and James Stewart all having career-best campaigns in 2021.
Kelly will be a flexible option in Rutten's rearguard this year, with the former Crow able to play on both small and tall attacking targets.
The Bombers currently have two free list spots available for the upcoming season, with Western Australia forward Nic Martin, Northern Territory prospect Ronald Fejo jnr and Tex Wanganeen - song club great Gavin - all training for an AFL list spot this summer.
The Pre-Season Supplemental Selection Period opened on Monday and will run until March 9.