Emilio Izaguirre has been ruled out for six weeks with a hamstring injury and will miss Celtic's Champions League Group G clash with Barcelona at Parkhead on Wednesday night.
The Hoops left-back came off during the 2-2 Clydesdale Bank Premier League draw with Dundee United at Tannadice on Sunday and Thomas Rogne is out for two weeks with a calf complaint picked up in the same game.
Winger James Forrest (hamstring) and strikers Gary Hooper (hamstring), Lassad (groin) and Georgios Samaras (ankle) missed the trip to Tayside and only the latter has a chance of making the game against the Catalan giants.
Celtic boss Neil Lennon said: "Izaguirre is out for six weeks. He had a scan yesterday. Rogne is looking at two weeks with a calf strain. James Forrest will be out for a week or two with a hamstring strain. Lassad has a groin strain.
"Samaras is hopeful but Hooper is very, very doubtful so we are a little bit stretched."
Lennon stressed the importance to his plans of Samaras, who scored in the 2-1 defeat in the Nou Camp last month.
He said: "It is hugely disruptive because they are big players and they have been for quite a while here and they would have been pivotal to the way we wanted to play tomorrow.
"However, we have good strength in depth and we will still have a very strong team to play tomorrow evening. But regardless of the other injuries, it is important that Samaras does make it.
"He has been very unlucky with injuries because his form has been excellent in the qualifiers and in the early part of the season. He had the bad elbow injury playing for Greece which set him back three or four weeks.
"He came back for the Barca game and played very well until he picked up the ankle injury so even if the rest of the players were fit, Samaras would have been very important to us and we are hoping he is going to make kick-off."