FREMANTLE recruit Harley Bennell's season is in jeopardy after suffering another setback in his rehab from a calf injury.

Bennell injured the calf playing in the WAFL the week prior to the first round of the season.

The Dockers placed the high-profile recruit on a long-term rehab program that was supposed to last 10 weeks.

Coach Ross Lyon confirmed on Thursday that Bennell had a suffered a setback but would not provide the exact details of the injury.

Lyon denied that there was anything suspicious about the nature of Bennell's unavailability.

"There is no mystery, Harley's had a calf injury - a significant one - and he's had a relapse," Lyon said on Thursday.

"There's no mystery, unless you want to attack it from a mischievous point of view.

"Harley's trained incredibly hard. Been fantastic. There's no mystery here."

The club is expected to release a statement later on Thursday providing further details on the injury.

"I'm not equipped with all the detail of it," Lyon said.

"He's hit a bit of a road block. But rather than me go off half-cocked ... I haven't got all the information."

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Lyon suggested that Bennell would need to go to the Australian Institute of Sport in Canberra to try and solve the issue. The Dockers sought consultation on Bennell's calf from AIS head of physical therapies, Craig Purdam, in April.

"I think (Geelong's) Mitch Clark's had a long-term calf similar to Harley's," Lyon said.

"He's gone to the AIS. Harley will probably end up at the AIS over the next few weeks."

Lyon said the Dockers were having a recurring problem with calf injuries this season. Skipper David Mundy has missed two NAB Challenge games and three home and away games with calf problems. Michael Johnson was ruled out of round one with calf soreness, however he is currently sidelined with a knee/hamstring injury.

Key defender Alex Silvagni is currently sidelined with a calf injury, and recruit Shane Yarran has also missed the last couple of weeks with a calf injury he suffered in his first game back in the WAFL.

Youngster Lachie Weller underwent a scan on his calf following the Hawthorn loss and underwent a fitness test at training on Thursday, which he appeared to pass.

Lyon said the club was reviewing the spate of injuries.

"Our bugbear is calves," Lyon said.

"We've got full faith in our team, but every program produces one area of weakness.

"For whatever reason, that's ours. I've got incredible faith in Jason Weber (Dockers sports science manager), Ken Withers and Peter Steele (club doctors) as a collective.

"They're working hard on it, liaising with everyone around the country and other clubs. Sometimes you've got to monitor your speed on the track, your volume, your overall work.

"We're reviewing our summer because we're not happy with it. We're on a bit of a knife's edge with it."

Lyon could not provide a timeframe on Johnson's return. He said Johnson and Aaron Sandilands were 'long-term' injuries and they would remain in the hands of the rehab staff for the time being.