Lai tore both his anterior cruciate ligament and medial ligaments on Saturday when Picken fell across his left leg .
Picken tried in vain to smother a goalsquare shot by Fremantle 's Michael Walters .
Lai tore both his anterior cruciate ligament and medial ligaments on Saturday when Picken , who tried in vain to smother a goalsquare shot by Fremantle 's Michael Walters , fell across his left leg .