Celtic midfielder Kris Commons will almost certainly miss Tuesday's Champions League visit by Ajax after coming off early at Hibernian.
Commons was his side's best player before being forced off with a hamstring injury during
"It's a huge blow," said Celtic manager Neil Lennon. "He's been fantastic this season, he's at the top of his game - you just don't see that one coming.
"We just have to see how it is in the coming days, but it doesn't look good."
The loss of Commons would increase Lennon's selection problems for the third match of their Group H campaign.
Celtic are already without captain Scott Brown after the midfielder's red card in the defeat by Barcelona.
Adam Matthews and Mikael Lustig both missed the visit to Easter Road through injury, meaning that 19-year-old Darnell Fisher was given his debut at right-back.
Left-back Emilio Izaguirre was also absent with an illness picked up on his way back from international duty.
"It's one of those that the player knows straight away and we got him off as quickly as possible," Lennon said of Commons before heading to the Netherlands to watch Ajax face Twente Enschede.
"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."
James Forrest came off the bench for a second week running as he continues his recovery from illness and the Scotland winger scored Celtic's equaliser.
"He came on sooner than expected, but he looks a lot stronger now," said Lennon. "Against Motherwell, he was just coming off the virus - he lost a stone.
"We are just hoping there's no reaction to those rigours of today and he will definitely be in contention for a starting place because he's a wonderful player and a match-winner as well."
Hibs had taken the lead controversially after a through ball from Kevin Thomson found Paul Heffernan in an offside position, but Lennon instead gave goalkeeper Ben Williams the credit for securing a point for the home team.
"He was clearly offside," said Lennon of Heffernan. "Our reaction was good. Officials get it wrong sometimes and I'm not going to point the finger at anyone.
"We played very well. (We) should have won the game and, but for the goalkeeper, he made some magnificent saves, we would have done."