The midfielder limped out of the draw against Fulham on February 24 with an ankle injury and missed the defeat at West Ham but returned to training this week.
Still absent are Christian Ziege (thigh), Jamie Redknapp (toe), Anthony Gardner (hamstring), Chris Perry (neck - back in training this week), Robbie Keane (knee) and Steffen Iversen (back).
And just to make matters worse, Dean Richards and Darren Anderton are both suspended.
It has stretched resources to the limit and youngsters Dean Marney and Jamie Slabber have been named in an 18-man squad.
Glenn explained this afternoon: "Gus has got a 50-50 chance of being fit but the long-term injuries are still there.
"Robbie isn't going to be fit for Liverpool but fingers crossed he'll be okay for Bolton.
"But we've still 27 points to play for and our ambitions are very much still to qualify for Europe."
Squad: Keller, Sullivan, Bunjevcevic, Carr, Doherty, King, Taricco, Thatcher, Thelwell, Davies, Etherington, Freund, Poyet, Acimovic, Sheringham, Marney, Toda, Slabber.
Gus Poyet has a 50-50 chance of facing Liverpool in Sunday's Premiership clash at the Lane.