Graeme Souness believes Rangers will find pressure heaped on them if they lose at Celtic Park on Saturday.
The in-form champions have won all five cinch Premiership fixtures this season and are two points clear of their Ibrox rivals at the top of table, following their 9-0 humiliation of Dundee United at Tannadice on Sunday.
Giovanni Van Bronckhorst’s side are also on a high after qualifying for the Champions League for the first time in 12 years but their 2-2 draw with Hibernian at Easter Road recently has left them already chasing Celtic.
Rangers take on Queen of the South in their Premier Sports Cup last-16 tie at Ibrox on Tuesday night, while Ange Postecoglou’s men travel to Ross County the following evening in the same competition but, after that, the focus will be on Parkhead and the first Old Firm game of the season.
Souness, who was player/manager at Rangers between 1986 and 1991, knows importance of the game and he told TalkSPORT: “Both teams are going into it with their tails up.
“No one, me included, expected Rangers to qualify for the Champions League. Their tails are up.
“My experience of working in Scotland is that you could be playing the best football, the best team, but you have drawn a daft game and you are in second spot to, in my case, Celtic.
“All the pressure is on you going forward.
“Celtic, at that time, could be playing not such good football but they are top of the league, they are off and running without any pressure on them.
“So this game is vital, vital because if Rangers were to lose, that would be them five points behind and then all the pressure comes on Rangers’ shoulders.
“Then Celtic could go on not playing very well week to week but as long as they are up there at number one, the pressure is off their shoulders and playing with a bit more freedom.
“This is a big game so early in the season.”
The former Liverpool and Scotland captain, who managed the Anfield side, Galatasaray, Blackburn and Newcastle – among others – still believes the Glasgow derby as an occasion takes all the beating.
He said: “It is the biggest derby. Galatasaray/Fenerbahce, Everton/Liverpool, Liverpool/Man United are enormous games but this tops it.
“Whether it is because Scotland has five million people, the spotlight, there is nothing else in the papers, the whole build-up to it, the pressure is very much on the players who go out and play.
“The whole country is looking at it and there is generally drama, generally some sort of thing that goes wrong for some individual or team.
“I come back to it. The last thing you say is ‘start right. Be on the front foot’ because if you go behind in that game it is hard to get it back.”