IT'S POSSIBLY the biggest unknown ahead of season 2017 – how will the rejuvenated Essendon list come together?

The Dons' fitness boss has revealed the return of the suspended players has proven challenging in terms of adapting a pre-season program to such diverse fitness levels. 

"The returning players are doing a great job - we’ve really got to the point where we’ve got 45 individual players because each of those returning guys did different amounts of work last year, they’ve all got different histories and they all respond to different types of training," high performance manager Justin Crow told the club's website. 

"To this point – with the exception of (Tom) Bellchambers – we’ve got them through the majority of the pre-season, which is really promising for the year ahead."

The Bombers are ramping up match simulation at training ahead of their first JLT Community Series match against Collingwood on February 16.

While Tom Bellchambers has been sidelined after knee surgery, the rest of the Essendon list is almost good to go. 

"The pre-season has been very good, certainly in the sense we’ve got the majority of our playing group through the majority of our pre-season," Crow said.

"We’re really pleased, given how many of the group are either young new players or returning players, how many of them are getting through most of our training load.  

"We’ll keep doing more and more match play in training, and match play drills, we’ll continue working on our high-volume work and continue to work on peak intensity training, which is basically getting up to the highest intensities that we see on match days."