Sheffield Wednesday are seeking a second opinion on the groin problem suffered by Gary Hooper in a bid to end the striker's nine-month injury ordeal.
Hooper was closing in on a first-team return after damaging his hip in December but reported a new issue after a 60-minute appearance for the Owls' under-23 team last week.
The 30-year has been ruled out of training with the senior side while his latest injury is checked out.
"He's not trained in full with the team this week," manager Jos Luhukay revealed. "He must go for a second opinion to another doctor.
"He still has pain and problems. It will take time to come back to 100 per cent in the team training.
"It's frustrating and disappointing for him but he must live with that."
Tenth-placed Wednesday, with four wins and a draw in their last six Championship matches, face table-topping Leeds United at Hillsborough tomorrow night.
They have been boosted by the recovery of centre-half Jordan Thorniley who limped out of the 2-1 defeat at Forest eight days ago.
"He's well," Luhukay confirmed. "He's trained as normal all week so we see no problem that he is available tomorrow."
The youngster may have to settle for a place on the bench after missing last Saturday's superb 2-1 triumph at Aston Villa where Tom Lees, Michael Hector and Daniel Pudil formed a three-man defence.
One player who will definitely miss out against Marco Bielsa's leaders is Sam Hutchinson, with Luhukay saying the midfielder still hasn't fully shaken off a groin problem.
"He tried to come back to 100 per cent but there are days when he has struggled," the boss said. "We must have patience.”