For 138 years, Rangers and Celtic have contested Old Firm games central to determining which half of Glasgow lifts the league title.
For the last four decades, that dominance has been uninterrupted.
However, with the emergence of a third force in Hearts, and potentially a fourth in Motherwell, the stakes are now higher than ever.
Sunday's Old Firm game - live on Your Site from 11am - could be just as much about eliminating a rival from the title race than staying in it.
Your Site duo Kris Boyd and Chris Sutton have weighed in on this colossal encounter...
"It is absolutely fascinating, nobody really saw Rangers slipping up on Sunday," Sutton said.
"They did well to retrieve it really at two down but if Sunday is a draw, then it's going to suit Hearts.
"At this moment in time with Celtic, and the way the season has gone, everybody or every sensible person would make Rangers favourites for Sunday.
"At this moment in time, with the nature of Celtic's season, the bad feeling from part of the fanbase and Celtic's club hierarchy, Rangers are in a better position.
"Rangers are a more harmonious club at this moment in time.
"There's a nervousness among the Rangers fanbase because they've got themselves back in a title race under Danny Rohl, whose record has been absolutely phenomenal, but they're still a team where they've got a slip-up in them - as proven at the weekend against Livingston.
"It is such a huge match because what's at stake and not just the rivalry on this occasion, it's really important for both teams that they want to win the game just to try and keep the pressure on Hearts."
"Whoever loses it, for me, is out of it, especially Celtic," said Boyd.
"I can't see any way back for Celtic if Rangers are to get the victory.
"Yes, they'll have that game in hand on a Wednesday night, but looking at it right now, Celtic or Rangers have to win the game to keep in contact with, or stay close to Hearts, because I do think they'll get the three points against Aberdeen on Saturday.
"There's going to be huge pressure on it. Rangers are at home. I don't think Danny Rohl has any problem in getting his team up for an Old Firm game anyway, but at home, I don't think there'll be any problem.
"The fans will be right behind the team, like we saw against Hearts. It's probably as vocal as we've heard a Rangers fanbase for a number of years at Ibrox. I don't think that'll be an issue.
"It's over to the players to go and put on a performance that leads Rangers to getting three points, but I'll say it again, whoever loses it is out of it."
"These last 10 games are going to be epic," Sutton added. "Regarding Hearts, I still make them favourites.
"Celtic don't have the strength which they've had in previous seasons. They have really got to up their game if they want to win the title.
"But I just can't see it for Celtic this season.
"Nobody really saw Hearts at the start of the season being in this position and people are thinking they're going to fall away, but why would they fall away? They've been at the top by rights all season.
"They've recruited okay in January, I don't think Celtic's recruitment has been on point by any stretch of the imagination, and Rangers have gone for a bit in January and recruited okay as well.
"I thought that it would be about the January 'arms race', who would get the better of that, and Celtic are bottom of that arms race.
"It's the best title race since I can remember from playing or doing the punditry work up there, it's absolutely fascinating. This could go any way."
"For Danny Rohl, the away form is now becoming an issue," said Boyd. "Especially in the run-in towards the end of the season when everybody's looking at the top six and Rangers will have three away games.
"It's going to be three difficult venues.
"You've got to look at it now. That's three away games in a row now where they've not picked up three points and it's not good enough at this stage of the season.
"You could look back in isolation at the Hibs game, in isolation at the Motherwell game and say, 'okay they may be good points in the context' but there's no way you can say that going to Livingston.
"No disrespect to them but they're a team that haven't won a game of football since August 9.
"Rangers, if they're going to deliver a title, I feel as if they have to be going there and winning.
"Yes you can point to bad finishing, good defending, good goalkeeping from Jerome Prior but I think overall Rangers have got to be going to Livingston and winning the game."
