That was the assessment of manager John Hughes as he prepared to take on the Glasgow giants without the steel and influence of captain Richie Foran.
The Irishman's knee injury required an operation in the summer and his recovery has been hit by minor setbacks. While Celtic's strength-in-depth is something at which Hughes can only marvel, he has mustered two opening wins and a draw to take initiative in the early season table.
Inverness have been a habitual thorn in Celtic's flesh as managers such as John Barnes, Martin O'Neill, Gordon Strachan and Neil Lennon can testify. Even with Champions League riches preoccupying Ronny Deila's Celtic, though, Hughes knows just how tough it will be to pull off another great shock victory.
"We have really been hampered by the injury to Richie Foran," Hughes admitted. "It's the same for us as Celtic missing Scott Brown. That's how important Richie is for us. We've had to adjust and ask questions of a lot of the other lads - and they have come through great so far. They have put in so much work from the first day of pre-season, and not just work - there's quality as well.
"It's our job to keep improving them individually and collectively - the education side of the game doesn't stop. But they have taken everything on board, right from pre-season. It's easier when you've got the sun on your back in July than when I first came here in November. You are trying to add your own wee bit to it and it's tough when the lads have to get a sweat up first. But it's just about taking on that great underdog spirit that Terry Butcher created here and has never gone away. Every manager wants to put their own stamp on it and thankfully it is working. All credit to the boys for taking it on board the ideas I've put across."
Hughes is on special alert for midweek hero Callum McGregor.
"They have had the strength of their convictions to keep McGregor in the team. He came up trumps again the other night and there's no doubt he's a lovely footballer. There is nothing better than someone coming through your own youth system."