Kris Commons remains on the sidelines as Celtic prepare for Thursday's Europa League clash against Udinese.
The midfielder has not started a match since the surprise home defeat to St Johnstone on 21 August.
The Scotland international has been dogged by a groin injury and has been suffering from illness.
"Kris has been ill as well, which is obviously a setback for us because he was so good for us last season," said assitant manager Johan Mjallby.
Commons appeared as a late substitute in Europa League group opener; a 2-0 loss at Atletico Madrid but has not been involved since.
"Kris has not really got the form of last season yet," added Mjallby.
"But he's training well and he's looking sharper and sharper, but his illness took him out of the game at the weekend."
Striker Gary Hooper was forced off with a leg knock during Celtic's 2-0 win over Inverness on Saturday but he has shaken it off in time to face Udinese.
James Forrest was on target against the Highlanders and Mjallby suggested the attacking midfielder would keep his place.
"I think it is going to be hard to leave James out," added the Swede. "James has been playing ever so well and has electric pace. He has been a very important player for us since the start of the season."
Celtic will be without the ineligible Badr El Kaddouri, while Emilio Izaguirre, Cha Du-Ri, Scott Brown and Kelvin Wilson are sidelined through injury.