Wigan Warriors second-row forward Joel Tomkins will be out for around six weeks after suffering a knee injury.
Wigan, who have lost in each of the last two Grand Finals, start the new Super League season at home to Catalans Dragons on Friday.
Dual-code England international Tomkins, 28, has scored 59 tries in 193 games during two spells with Warriors.
He started his career at Wigan and returned in 2014 after a three-year spell in rugby union with Saracens.
Tomkins' younger brother Sam, who is back at Wigan after a spell playing for New Zealand Warriors in the NRL, will also miss the start of the season because of a knee problem.