In the latest Off Script, Graeme Souness provides a fascinating insight into the Old Firm, and the big mistake he made when arriving at Rangers.
Souness, who was player-manager at Ibrox between 1986 and 1991, won the Scottish title in four of the five years he was at the club, having spent two years at Sampdoria following huge success at Liverpool.
In the latest edition of Off Script, Souness speaks with Pat Davison about how he initially underestimated what the game means in Glasgow, and why being a player-manager for a top club now would be nearly impossible.
Watch Rangers vs Celtic from 11am on Sunday on Sky Sports Football and 11.30am on Sky Sports Main Event; kick-off 12pm.
'I changed my view in 10 minutes'
Fortunately, when I was up in Scotland for five years, we were bossing it for four of them.
But I got criticised, greatly criticised, for saying: "I don't care if we lose to Celtic as long as we win the league." That did not go down well.
Did my view change on that? Oh yeah. In the first 10 minutes of the first Old Firm game! My thinking was: 'As long as we end up with our hands on a cup at the end of the season, I don't mind taking a few blows along the way.'
But then you get it. These games mean so much. And you generally end up winning the league if you win these games.
I'd been announced before the end of the 1985/86 season, and there was a Glasgow Cup final, essentially a charity match between Rangers and Celtic. That was full on, in a game that shouldn't have been full on. It made me realise how important these games were to the supporters.
Then you get into the real stuff, the competitive stuff.
- Off Script: Carra's standout team talks
- Off Script: Nev - Teams should broadcast training!
- Off Script: Carra's pre-season tales
It's not just the points you get on the day. What I found was you could be playing the best football, but you'd be second in the league because you dropped points or drawn a daft game, and you'd go into an Old Firm game and all of the pressure would be on you, despite the fact you played better football.
It's all about winning these games and staying top. I found that being top put all the pressure on second place, not first. The focus is on the second-place team, who can't afford to slip up again. You have to be winning these games to take the pressure off you.
There's a week of extreme criticism on the team that loses that game, and many times it's not deserved. That puts them under pressure and frees you up to go out and play with a bit of freedom.
Rangers are getting nearer. Celtic on paper arguably have the better players, but that counts for nothing in many cases.
I think the first Old Firm this weekend will be very close again, and I'm hoping Rangers can edge it. Celtic are going for nine in a row, as a Rangers supporter I don't want to know about that! We've somehow got to bring that to an end.
'Player-manager today? Nearly impossible'
With Vincent Kompany's recent struggles as player-manager at Anderlecht in mind, Souness says it is extremely difficult to juggle both roles in modern football.
It's very difficult. Extremely difficult. When you're a player, you only really have to look after yourself. And then you go into management, and you've got 30 players' welfare to keep an eye on.
The non-footballing side of things, which at that time as player-manager I had to get involved in, was all-consuming and very, very difficult. On top of that you have to stay fit to perform on a Saturday.
A great deal depends on the support you have around you. In my case I had Walter Smith, who was a great help to me, and the chairman and other people at the club. I had enormous help.
But Celtic are a big football club, Rangers are a big football club. The pressures involved with managing them alone are enormous, but to try and play as well today would be nigh-on impossible.
I'd say at any big club today, it would be nigh-on impossible, because of what is involved in football nowadays.
'Everything is off the cuff'
Souness, a pundit at Sky Sports for over a decade, also gave an insight into how he approaches analysis on game day.
You turn up at a studio, and the bigger the game, we all get excited about them. You turn up with a backstory; who's under pressure or who may be the star of the show. You turn up with some thoughts in your head but it very rarely turns out how you anticipate.
I think the way we deal with the big moments is better than anybody else, and we have some talented young men and ladies working in our business now.
The game gees us up. If there's lots to talk about, it makes our job very easy.
In big moments, am I best when I've thought about what I say, or when the story just takes me over? Without a doubt, everything is off the cuff.
I could trot out all sorts of stats, but so could the viewers at home. You can Google how many goals a player has scored in the last few seasons, or against this particular side, but our job is to point the viewers to something that is happening in the game that they may not have seen or thought of.
Of course you must prepare in terms of knowing the players, and what form they're in, but in the 90 minutes, a lot of it is to do with what I see.
How to watch Rangers vs Celtic
Rangers host Celtic in the first Old Firm clash of the season this Sunday and you can watch all the action live on Sky Sports.
Join us live from Ibrox at 11am on Sky Sports Football - coverage begins at 11.30am on Sky Sports Main Event - or follow our dedicated match blog online. Kick off is at 12pm.