FREMANTLE's injury toll continues to grow with young key position utility Tanner Smith ruled out for six-to-eight weeks with a hamstring injury he suffered in Saturday's win over Port Adelaide.

Fellow youngster Brady Grey (ankle) and veteran midfielder Matt de Boer (knee) are also set to spend extended periods on the sidelines after sustaining injuries while playing in the WAFL on Sunday. 

Smith injured his hamstring while being tackle in the third term of the win over Port. It is a bitter blow for the 22-year-old. He has played just four games in four seasons on the Dockers' list. 

He was a second-round draft pick in 2012 and made his debut in 2013, playing just one game for the season, but was delisted at the end of 2014 and re-drafted as a rookie. 

Smith played one game in 2015 in round 23 when the Dockers rested 12 senior players. Injuries granted him an opportunity in round 12 this year and he impressed against the Lions to the point where he retained his place last week against Port.

Grey, 20, has only played three AFL games including two earlier this season and had been pushing for another opportunity. He gathered 20 disposals for Peel on Sunday but he sustained an ankle injury late that is set to sideline him for six-to-eight weeks.

De Boer has been ruled out for the next four-to-six weeks with a knee problem. The 26-year-old has played 136 matches for the Dockers in eight seasons but has managed just two games this year.

He has spent most of the year in the WAFL, averaging 30 disposals per game.

He is set to become an unrestricted free agent at the end of the season when his contract expires.