A TRIMMED-down Sean Darcy is set to improve on a promising debut campaign after the young Fremantle ruckman returned to pre-season slimmer and stronger.

The Dockers' primary big man, Aaron Sandilands, was limited to 10 games for the year after suffering multiple right hamstring injuries.

Darcy was forced to take on a huge workload for someone drafted at No.38 in 2016 but thrived, showcasing an imposing physical presence.

The 19-year-old told reporters on Friday he was in better shape, having tipped the scales at 111kg last year.

"My skinfolds have gone down a fair bit. It's more staying light, running-wise, then in the gym building my strength up to compete with the bigger boys in the AFL," Darcy said.

"My skinfolds are improving and my strength in the gym has definitely gone up."

It was important for Darcy to lose weight to be able to run out matches against aerobically elite ruckmen, and that is his main goal for the pre-season.

"I want to improve on my fitness so I can run out games better and go with the best runners in the AFL," Darcy said.

Another focus will be improving his play in attack. With 34-year-old Sandilands having signed on for 2018, Darcy will need to bide his time before he can take over the No.1 ruck mantle.

In the meantime, he wants to help the second-lowest scoring side in the competition kick more goals.

"I want to be more than just a one-position player. The AFL is growing from when you could just have one position. You've got to have a range in your repertoire," Darcy said.

"I've got to work with the forwards on my leading patterns and my running around there. I want to develop my forward game as much as my ruck game."

Being more accustomed to the AFL environment should help his development.

"The first year, you’re a bit unsure about everything that's happening, with everything coming at you at once, whereas now you're in the swing of things and you know what each day's going to be like," Darcy said.

"Now it's nailing down all of my specifics, like (coach) Ross (Lyon) told me at my exit meeting, and just developing my game as much as possible."