Leeds Rhinos centre Kallum Watkins has been ruled out for six months after rupturing his anterior cruciate ligament.
The 19-year-old picked up the serious knee injury during Sunday's 26-20 defeat at Huddersfield Giants.
Leeds' defence of their Super League crown has got off to a turbulent start as they have lost three of their six opening games are currently without a host of injured key players, including Carl Ablett (ankle), Scott Donald (shoulder), Greg Eastwood (wrist) and Kevin Sinfield (dead leg).
"This is extremely disappointing news for Kallum and we wish him a speedy recovery," coach Brian McClennan told the club's official website.
"Our medical team will ensure that he receives the best possible care and I am confident he will come back from this set back so early in his career.
"Having spoken to Kallum he is prepared to use this as a challenge to overcome to help him become a better player and I think that speaks volumes for the type of young man he is."