Hull Kingston Rovers half-back Danny McGuire will be back in a minimum of eight weeks after he was diagnosed with a blood clot in the leg, says head coach Tim Sheens.
McGuire, 35, has been limited to 10 appearances by injuries and concussion since his winter move from Leeds.
The latest issue arose during the 54-18 defeat by Wakefield this month.
"We initially thought three months, it looks like only eight weeks," Sheens told BBC Radio Humberside.
"It's a difficult one, it's not really an injury, it's a clot in the leg, which is unusual and very dangerous.
"The treatment needs to be very sensitive and so is the return, there's a certain amount of blood thinning and you can't afford to get knocked around at training and lose blood or you could be in big trouble.
"I think it's as we go, it's going to be a minimum of eight weeks. We were facing as long as the season and a danger to Danny's health, so with any luck it will be a shorter turnaround and until we're 100% we're not going to play him."
More injury concerns at Rovers
Sheens' problems have been further compounded by injuries to centre Junior Vaivai, and on-loan St Helens hooker Aaron Smith in Sunday's Magic Weekend derby defeat by city rivals Hull FC.
"The scans will tell us about Junior," Sheens added.
"I don't think it's an ACL which was the biggest fear because he's had three of those already and it would have been career-ending. I won't panic until the scan.
"It's a five day turn around for the Wigan game, and Aaron's loan was up anyway so we would have had to ask St Helens about a renewal, which we will do.
"But in real terms he can't play next week, it's a seven-day thing when you come back from a concussion."