Midfielder Edu travelled to Spain this morning but is not sure of a place in the squad for tomorrow night's game.
The USA international took a kick to his calf during Saturday's 1-1 Clydesdale Bank Premier League draw with Inverness and has still to shake off the stiffness.
"It's getting better but I still haven't tested it out yet," Edu said.
"We'll see how it is when I get out there and see if I can train or not. It's feeling a bit better but I'm just hoping to be fit for tomorrow.
"I would say 50/50. Obviously it's a big game and I want to be a part of it, so fingers crossed."
Fellow injury worry Vladimir Weiss, who was taken off at half-time on Saturday with a heel problem, also travelled to Spain.