Widnes Vikings captain Kevin Brown has been ruled out for up to six weeks with an ankle injury.
The 30-year-old stand-off has been in superb form this season, scoring 16 tries in his 15 appearances.
Brown joined the Vikings from Huddersfield in 2013 and the former Wigan man extended his contract until 2018 at the start of the month.
"It's pretty tough to take, really," Widnes head coach Denis Betts told BBC Radio Merseyside.
"At this stage of the year it's a tough one not just for us, but for Kevin himself, as his form this year has been fantastic."