HARLEY Bennell has advanced to "high-end sprinting" at training and will be used in a similar role to speedy Hawthorn superstar Cyril Rioli upon his return to football, according to Fremantle coach Ross Lyon.

But Lyon said the Dockers are holding their breath before putting an exact timeframe on Bennell's long-awaited comeback.

The 24-year-old former Gold Coast midfielder was sidelined for all of last season due to right calf problems and was sent to Germany for specialist treatment in December after hurting his "good" left calf at training. 

Bennell has been gradually building up his running workload since and Lyon confirmed he remains on track to return via WAFL club Peel Thunder during the first half of the season.

"He is high-end sprinting. He is feeling really good. From here it is just about volume of sprinting now," Lyon told The West Australian.

"It is as confident as we have been in his body but we are still jumping a few hurdles. 

"We are, for Harley, holding our breath because he has worked so hard. But we also know how important he is to us.

"When he comes back - if he keeps progressing - he will play early rounds. Is it (rounds) four, five or six? I am not exactly sure.

"It certainly won’t be any earlier. It could be around there. It could be a week or two later." 

Lyon conceded Bennell wouldn't have the conditioning to play on the ball upon his return. Instead, his likely role will be in attack with bursts in midfield - in a similar vein to Rioli. 

"That is what we envisage with Harley. He can play close to goal and he can free up (Nat) Fyfe to go forward for periods by going midfield for five or six minutes," Lyon said.

"He will be an offensive threat and give us some real speed in our front half."