HARLEY Bennell will be wrapped in cotton wool until pre-season training commences after Fremantle ruled him out of Peel's WAFL finals campaign.

The injury-plagued star was one of 18 Dockers eligible for the Thunder's finals series assessed by medical and fitness staff this week.

After six games back from repeated calf setbacks, including two at AFL level, Bennell was expected to continue playing through the WAFL finals.

Fremantle took the step of naming Bennell in Peel's reserves team in July, even though he was only watching from the grandstand, in a bid to qualify him for finals.

But now the Dockers have pulled the 24-year-old out of September action, deciding rest is in the Bennell's best long-term interest.

"It was a successful return to playing and we certainly saw signs during those six games of what Harley is capable of delivering next year for the club," general manager of football operations Chris Bond said.

"We have 18 players qualified to play for Peel in the WAFL finals and they were all assessed by our medical and fitness staff yesterday.

"Following that process, our medicos and fitness staff advised that it was in Harley’s long-term playing interests to be rested now, which will also give him the best lead-in to day one of our 2018 season.

"We believe that a rest now followed by an uninterrupted pre-season, Harley will be right to go for round one of the 2018 season."

Bennell played his first game for 16 months for Peel in mid-July and the ex-Sun booted two goals on his Dockers debut in round 22 against Richmond.

He then had 13 touches and kicked a goal last Sunday against Essendon.

Bennell has been limited to playing in attack since his comeback, but the Dockers hope to unleash him in a star-studded midfield next season.

Meanwhile, first-year defender Luke Ryan and tall Brennan Cox have been ruled out of Peel's qualifying final against South Fremantle this Saturday due to groin soreness, however they are expected to be available for the remainder of finals.

Peel is restricted to fielding a maximum of 15 Dockers in any finals match after a rule change implemented this year.

The Thunder had 17 Fremantle-listed players feature in last year's maiden Grand Final victory over Subiaco.