FREMANTLE ruckman Sean Darcy has benefited from a re-worked running program and built the best fitness base of his career as he prepares to lead the Dockers' ruck brigade in his fourth season.

The arrival of new high-performance manager Phil Merriman has seen the Dockers overhaul their summer running program and Darcy said he was covering the ground as well as he had in recent seasons.

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The 22-year-old is performing better in the ruck as a result as the Dockers work through plans to again pair Darcy with versatile teammate Rory Lobb and rotate the duo forward in 2021.  

"I feel like I'm covering the ground a lot better. I'm not as tired in training, I'm thinking a lot more clearly, and I'm making the right decisions," Darcy said on Wednesday. 

"There's obviously a lot more work to go, which is good, but I'm feeling a lot better.

"We're not doing the same running that we used to do last year, so it's been a really good change.

"I feel like I'm running really well … I feel a lot fitter."

Darcy used his off-season last year to link up with teammates – including a number of strong runners – and train in Perth, building his fitness ahead of the start of pre-season.

He returned home to Victoria over Christmas but was able to train with quarantined teammates when he returned to Perth, with new assistant coaches Matthew Boyd and Joel Corey leading the sessions.

His focus now was to avoid the pre-season setbacks that have plagued his short career, including calf, shoulder and ankle setbacks during the build-up to the 2020 season.

"My approach has just been to get as fit as possible and make sure I'm healthy and out training every training session," Darcy said.

"I've had a lot of pre-seasons where I come back fit and then I break down in January and I'm out for eight weeks and it really affects you during the year."

Darcy described this pre-season as the most intense of his four at the Dockers since being drafted with pick No.38 in the 2017 NAB AFL Draft.

He has worked closely with fellow ruckman Lloyd Meek, who has added size in the off-season, and retired club great Aaron Sandilands, who remains at the club as a part-time ruck coach. 

The duo completed stoppage work with Sandilands during Wednesday's session in Perth's 30-degree heat, while a number of key players had light sessions.

Star forward/midfielder Michael Walters continued to train away from the main group, completing the warm-up before running and kicking with midfielder Darcy Tucker, who suffered a serious hamstring injury last July.

Key defender Alex Pearce, who recently returned to training after recovering from an ankle injury, had a light session and kept to a cross-trainer and bike alongside Sam Sturt (ankle) and recruit Brandon Walker.  

Defenders Griffin Logue and Tobe Watson trained away from the main group with draftee Nathan O'Driscoll, who arrived at the club with a shoulder injury, and speedster Stefan Giro, who is returning from a knee reconstruction.