The Scotland international, who came off the bench during Tuesday's home defeat by Cluj, said: "The fans are more hurt than we are and rightly so, they pay good money to come and watch and expect us to get to the Champions League.

"It is very difficult to get there but the fans' expectations of us have grown over the past couple of seasons.

"I don't think they will be happy. Am I expecting a sell-out crowd? No. But they are entitled to show their frustration and it's up to us to go and put on performances again to put bums back on seats."

Griffiths has been at Parkhead since January 2014 and understands how the Celtic fans will respond to their European disappointment.

But he does not feel any need to tell any of his new team-mates what to expect.

"They will quickly know the demands of the Celtic support," the former Livingston, Dundee, Wolves and Hibernian player said.

"I had to learn quickly. If you can't handle the demands of being a Celtic player then you will not be here very long.

"But I believe in every single one of the players through there that they have the heart and desire to be a Celtic player and meet the demands that everyone expects.

"I knew when I came here how big a club Celtic was and when I joined I think they were on a 19-game unbeaten run and 20-odd points clear in the league.

"I remember going to Aberdeen and getting beat and even though we were 27 points clear, the gaffer (Lennon) came through us like a ton of bricks. That's the demands the gaffer sets.

"That has filtered right the way through. When he was a player, he would have had demands on himself and the manager would have had demands on him, and it just transpires all the way through."