BROWNLOW medallist Tom Mitchell continues to make "rapid" progress from his broken leg and could make a shock playing return this year, a leading sports doctor says.

The Hawthorn champion broke the tibia and fibula bones in his left leg in an innocuous training incident on January 12 but was walking unaided up the Waverley Park steps only 19 days later.

Mitchell is already doing some weight-bearing rehabilitation seven weeks post-injury, completing squats with a kettlebell in the club gym.

The Hawks have consistently stated in recent weeks the 25-year-old will miss the entire season.

They can replace Mitchell via the pre-season supplemental selection period, which ends on March 15, or the mid-season draft and still bring him back to play if he were ready late in the year.

World-renowned sports medicine specialist Peter Brukner told Mitchell remained unlikely to be part of Hawthorn's 2019 campaign unless "everything went absolutely beautifully".

His typical recovery period would be about six months, but Brukner, the Australian cricket team's and EPL club Liverpool's former doctor, said the time out depended on the individual.

"It does seem interesting that it's been so rapid," Brukner said of Mitchell's increased activity.

A lot depends on the individual and, in particular, the way their bones heal. Some people's bones heal very quickly, whereas others are much slower to heal
"I can only assume they've been scanning and reviewing him regularly and he's making very good progress, which is why they've been happy to allow him to do things like squats and so on."

Brukner said there was a shift in the past decade towards encouraging people to move earlier after these types of injuries, but that doesn't necessarily mean a shorter recovery.

"We're less concerned about damage early on, so getting them moving sooner makes it a more gradual build up," he said.

"If you do nothing for six weeks or three months or whatever, then all of a sudden you've lost all that fitness and loading and so on.

"We know that some sort of gentle loading of the bone actually stimulates healing."

Mitchell's next step will be to run on the AlterG anti-gravity treadmill, a milestone that will likely be reached about the three-month mark post-injury.

He would likely spend another month of increasing force on the treadmill before being ready to run on a football field, Brukner said.

Mitchell would still be a couple of months away from returning even after graduating to that stage.

"The metal in his leg is holding everything together and they're happy for him to walk and take some weight on that, but it's a very different matter to actually running on it," the doctor said.

"So while it might seem, 'Wow, he's going incredibly well', I wouldn't get too carried away or optimistic about it.

"It's unlikely he would be back in full training prior to six months, but if everything went really well he might just get in at the end of season.

"But that will be a decision down the track depending on his progress and where the team's at."