Smith badly tore his hamstring in the opening half of Peel Thunder's 19-point loss to East Perth.
The 20-year-old key position player made his AFL debut in round four last season against Hawthorn at Aurora Stadium but did not play again due to a serious shoulder injury and will now be sidelined for up to two months.
Duffy, an exciting small forward who is yet to make his AFL debut, dislocated his left collarbone. It is a major blow for the 19-year-old who had shown great promise during the pre-season, according to Fremantle football operations manager Chris Bond.
"It's disappointing for us. He was going really well," Bond told 6PR on Monday.
"He’ll be in a brace for a few weeks and then we’ll go from there."
High-profile recruit Colin Sylvia was also withdrawn from the Peel side at half-time after collecting 12 disposals.
Sylvia experienced tightness in his quad but Bond believes it was not overly serious and expected he would not miss any games.
