Prop Lillyman, 27, tore his right bicep off the tendon in the opening exchanges of the Warriors 26-10 trial victory over Gold Coast on Saturday.
“It’s probable he’ll have surgery this week,” said club doctor John Mayhew.
“With this type of injury he faces three months on the sideline.”
Lillyman was a key member of Warriors squad last season helping them reach only their second ever NRL Grand Final
“It’s a real blow to lose Jake and it’s especially tough for him,” said coach Brian McClennan.
“It’s disappointing knowing how hard he has worked during the off-season and how well he has prepared but I know our medical staff will do everything they can to give him the best possible treatment and get him back just as soon as possible.”