Former Celtic hero Kris Commons insists he can still detect some "vulnerability" in the Rangers camp on derby week.
And he believes Sunday's meeting at Ibrox is their last chance to turn the title race around.
Ange Postecoglou's Hoops have been top of the Premiership ever since a statement 3-0 win under the Parkhead lights on February 2.
Their three point advantage could be wiped out by a home win this weekend and Commons expects Giovanni van Bronckhorst to go for the jugular.
But he insists a second straight home defeat to their closest rivals will inflict "psychological damage" on the champions.
Writing in his Daily Mail column, Commons said: "It's not just the fact that Celtic would go six points clear. There are a few different things you have to consider in all of this.
"It's the psychological damage they could inflict on Rangers if they were to beat them on their own patch on the back of that Celtic Park annihilation.
"There's also the fact that Rangers are still juggling their domestic ambitions with trying to make further progress in the Europa League.
"Even beyond next week's game, I still feel there's a vulnerability to this Rangers team domestically and I sense that they could drop more points from now until the end of the season.
"I don't get that same impression from Celtic at the moment. They look extremely slick and well-drilled. Postecoglou has created an animal.
"If they do go on and become champions, I feel it would rank as one of the sweetest league titles in Celtic's history, given the shambles the club were in last summer."
Commons has told Postecoglou to lean on experienced heads such as Callum McGregor and Joe Hart if they hit a sticky patch – and reckons Neil Lennon's derby day advice could come in handy.
He added: "For Rangers, it's a game they simply cannot afford to lose as they look to defend their title.
"Giovanni van Bronckhorst is an experienced operator. He knows how things work in Glasgow and he knows the pressure that he and his players will be under on Sunday to right the wrongs of the defeat at Celtic Park last month.
"I expect Rangers to go full throttle and try to unsettle Celtic in the early part of the match. Their fans will demand them to get on the front foot.
"It will be a big test for the Celtic defence and the likes of Carl Starfelt and Cameron Carter- Vickers. They have both improved steadily as the season has gone on.
"But, particularly in European games, Celtic have been exposed at the back too easily. Rangers will look to play on that and maybe plant some doubts into their minds again.
"That's where the likes of Callum McGregor and Joe Hart will be key in the spine of the team. If Celtic start having a wobble at any point, they need to use their experience to calm things down.
"Going away from home as an Old Firm player pitches you into an environment unlike any other. Neil Lennon always used to tell us to be 'ice cool' and to take the sting out of the game.
"But that's sometimes easier said than done. I remember a few games where I literally couldn't hear some of my team-mates when they were stood only a few yards away from me on the pitch.
"The noise is deafening and that's the cauldron Celtic must prepare themselves for this weekend. Rangers will be coming after them because, from their point of view, it's probably last-chance saloon."
