Celtic manager Neil Lennon admits the loss of Kris Commons for the Champions League clash with Ajax at Parkhead on Tuesday night is a "huge blow" to the Hoops' qualification hopes.
Celtic go into the game still looking for their first Group H points after two games, and will be without their star midfielder who was replaced by James Forrest in the 1-1 Scottish Premiership draw against Hibernian at Easter Road after pulling up with a hamstring injury.
The Scottish champions will also have to do so without captain Scott Brown who was handed a three-match ban after being sent off against Barcelona at Parkhead earlier in the month, flicking a leg out at Neymar after he had fouled the Brazilian.
Although Celtic have indicated they will appeal against the severity of the punishment, Brown is certain to be out for the visit of the Dutch side.
Lennon will also be without Adam Matthews, sidelined for three months with a shoulder injury, but is confident that right-back rival Mikael Lustig, who missed the trip to Leith with a hip injury, and left-back Emilio Izaguirre, who was out with illness, will be fit.
The Celtic manager has all but written off Commons for the game.
Lennon said: "Kris knew straight away, he felt a pull.
"We don't think it's a tear but if it's a strain it's at least a couple of weeks so it's not looking good for Tuesday.
"You can't tell how they are until they settle down but players more or less know straight away.
"It's a huge blow. He's been fantastic this season, he's at the top of his game, in great physical condition - you just don't see that one coming.
"He just stretched for a ball and felt something.
"So we've got one going out and one coming in in James Forrest who's a brilliant player, and showed it again today.
"We'll have to assess the squad ahead of Tuesday. We're very hopeful Mika will be fit, Emilio should recover as well.
"We've obviously got a problem in midfield with Scott missing, and now Kris, so we'll see what we've got.
"I think we can beat Ajax at home but I don't know what personnel I'll have.
"This is the problem when you have players away for two weeks over long distances. I'm glad the international break's over, I'm glad that game's out of the way.
"You could see some of the players who had been on duty were a bit heavy-legged.
"It doesn't do us any favours, obviously, but I was very pleased with the performance.
"We go into the game on Tuesday confident."