RUCKMAN Aaron Sandilands has extended his stay at Fremantle until at least the end of 2016, as one of three Dockers to agree to contract extensions with the club.

The four-time All Australian big man was out of contract at the end of this season, but has committed to a one-year deal.

Matt de Boer has also signed a one-year contract extension, while Jon Griffin, seen as a possible longer-term replacement for Sandilands in the ruck position, has committed to two more years beyond 2015.

Sandilands' signature gives the Dockers another boost after their stellar start to the season, which saw them defeated for the first time on Friday night by Richmond.

The 32-year-old ruckman has been a significant factor in the Dockers' form, setting two records in recent weeks for the most hit-outs in a game and also most hit-outs to advantage.

He said his body was coping with the demands of his 13th AFL season and hadn't contemplated looking elsewhere.

"It's where I got my start," Sandilands told the club's website.

"I'm keen for success, it was easy to (choose) to stay. I feel like my body is in pretty good nick at the moment and to get another 12 months with these guys has made me really happy."

Fremantle list manager Brad Lloyd said it was crucial for the club to have re-signed two of its ruckman, saying Griffin, who arrived at the club in 2011 from Adelaide, remained part of its plans.

"[Griffin] is an important player on our senior list," Lloyd said.

"It is pleasing to have signed both Aaron and Jon, securing a couple of our ruck stocks for the coming season."

De Boer has played six games this season for a total of 121 since making his debut in 2009.