ADELAIDE defender Nathan Bock has taken a big step in his comeback from a niggling heel injury, running pain-free for the first time in almost five months.

Bock, 26, missed the last six games of the season after coming from the ground against Geelong in round 18.

He tried desperately to return for the Crows' finals campaign, even training with the team before declaring himself unavailable for selection.

The microfracture in his foot didn't heal as expected in the off-season and Bock was forced back into a moon boot to minimise stress on the area.

Bock was restricted to light duties when Adelaide returned for the start of pre-season training in mid-November, but physical performance manager Stephen Schwerdt said the 2008 best and fairest winner had made solid progress in the week leading into the Christmas break.

"Bocky's had a few running sessions and he's going really well," Schwerdt told afl.com.au.

"We're taking it relatively conservatively with him just to make sure. We wanted to make sure he was spot on before we got him into any running and so far, so good."

Schwerdt said he expected Bock to be back in full training by mid to late January.

"We'll steadily progress Bocky over the next few weeks," he said.

"The couple of weeks while the other guys are on leave will be pretty important to Nathan, so he'll keep training and doing work around the club."

Onballer Nathan van Berlo will also be expected to ramp up his training load after Christmas.

Van Berlo joined Bock in the stands for Adelaide's two finals after experiencing back soreness in the round 22 win over Carlton.

He was diagnosed with stress fractures and hasn't been able to run since.

Young teammate Patrick Dangerfield developed a similar condition last season, but was sidelined for just two weeks.

Schwerdt said the chronic injury, usually associated with fast bowlers in cricket, was more common in AFL players than people might think.

"There have been a few guys over the journey who have had stress fractures in their back," Schwerdt said.

"Depending on how their body reacts, some guys can get by and play and it doesn’t seem to be an issue with them. Other guys have got to take a slow approach and Nathan's been like that.

"It's stirred up a bit by their training. It is a repetitive [use] injury, but a bit of it's also traced back to genetics and how people are put together because all the players are doing similar work."

Dangerfield said his injury was ongoing but he was learning to better manage his body so that he didn't have the same problem next year.

"It's all about injury prevention and management because it's not something that's going to go away straight away," he said.

"I still get pretty sore every now and then, but I've got to get on top of it with my pilates and core-strength training.

"My stress fracture has cracked right through now, so that should help with the healing. It makes it sound worse but it's actually a good thing."