FIRST-YEAR sensation Will Ashcroft has ruptured his anterior cruciate ligament, bringing his excellent debut season to an end.

The 18-year-old, who has played every game since being selected with pick No.2 in last year's draft, injured his right knee in a tackle during the fourth quarter of Saturday night's 11-point win over Geelong.

He hobbled off the ground and was subbed out of the match.

Ashcroft was nominated for the competition's Rising Star award in round two, and is among a handful of favourites to take out the award due to his consistent performances in the Lions' midfield.

Brisbane confirmed the diagnosis on Sunday morning.

"We are all hurting for Will because you never want to see any player experience a serious injury, especially a player in their first season,” the Lions' footy boss Danny Daly said.

"Our main priority is for everyone at the club to wrap their arms around Will and do everything we can to support him and his family in any way we can.

"Will is super professional in everything he does, so we know he will do everything he can to recover from this."