Scott Brown will undergo a scan on Monday to determine the extent of the injury he suffered against Rapid Vienna.
The Celtic skipper pulled up sharply in the first minute of the friendly and was stretchered off after a two minute delay.
Any type of hamstring injury is certain to rule the midfielder out of both legs of the Champions League qualifiers against KR Reykjavik as well as deny Brown a vital part of pre-season conditioning.
Looking at the injury Ronny Deila told the Celtic website: “He got an injury and we think it was his hamstring, but we don’t know yet how severe the injury is. Hopefully it’s not big and he will be back quickly. He will have a scan tomorrow and we will see what happens.”
Beram Kayal replaced Brown but after seven minutes Celtic went a goal behind when Virgil van Dijk glanced a header from an inswinging free-kick past Lucasz Zaluska.
Celtic should have drawn level on the half hour but Derk Boerrigter missed an open goal after being set up by Anthony Stokes but the visitors equalised in the 70th minute when substitute Teemu Pukki scored from a Leigh Griffiths pass.
With just over a week to go before Celtic fly to Iceland the noisy crowd and testing conditions provided the hoops with a good test ahead of next week’s Champions League qualifier.
Despite a fairly impressive display Deila would have preferred to have seen more from his player.
“There wasn’t enough energy in the game,” he said. “We didn’t create enough and didn’t have the ball enough, so there is a little bit of disappointment but it’s very early and we need to train well and get in good shape so that was the positive. We had a good game, with a good crowd and it was good training for the Champions League.
“There was good energy late on. We had 15 minutes in the first half and 15-20 minutes in the second half which were ok, but we need longer periods with more energy and attitude.
“It was 30 degrees outside and it was very hot so I understand it. We will have another game on Tuesday, so there will be an opportunity for the players who didn’t play so much today to play in the game and it will be a good match for us.”