Warrington are still waiting to learn the full extent of Chris Sandow's hamstring injury.
The 27-year-old Australian was injured during the first half of the Wolves' 26-18 win over Wigan at the DW Stadium on Friday and will see a specialist in London on Monday night.
"He's got a substantial grade-two tear," said Wolves coach Tony Smith.
"He's going to be out for a while and, although it's not a week-or-two injury, we won't know the length of time until he sees a leading expert in London and finds out what his options are in terms of either repairing or rehabilitating it."
Utility back Stefan Ratchford is likely to step into the scrum-half role for the visit of St Helens to the Halliwell Jones Stadium on Friday and Smith also has the option of playing young half-back Declan Patton.
But he admits the loss of former Parramatta half-back Sandow, who has played a key role in lifting Warrington to the top of the Super League table, is a major setback.
"We've got some options, which shows our depth, but it is a blow for Chris and us and also for the game because he's been in the form of his life," Smith added.
"If there's been a better player in Super League this year, I haven't see him. The way he's lit up the competition has been breathtaking. He's raised everybody's excitement levels, they've all been able to appreciate his brilliance at times.
"Hopefully he won't be out for too long and he can get back to producing some of his magic."
Smith received some better news on the injury front after centre Rhys Evans, who missed most of last season with a shoulder injury, was cleared of a similar problem.
"Rhys felt something pop in his shoulder and feared the worst but it was a (synovial) bursa or sac of fluid that had burst," Smith said.
"It has settled down really well and he could be a chance for this week."