The late, great Tommy Burns summed it up well. Asked to describe the nature of the storied Old Firm rivalry, the former Celtic midfielder and manager claimed it’s the only match “in the world where the managers have to calm the interviewers down.” Graeme Souness echoed that sentiment by insisting “it isn’t just another game.” There are countless derbies around world football, but few carry the weight of the fixture between Celtic and Rangers. Few have captivated so many. There are some Scottish football fans who baulk at the notion of the Old Firm rivalry being Scotland’s defining fixture, but there’s no real argument to the contrary. Celtic and Rangers are the two biggest, and most successful, clubs in the country. On top of that is piled high an intertwined mass of political and religious factors that mark out the Old Firm rivalry as one of the most complex, and compelling, games in world football. Even those unfamiliar with the intricacies of the Scottish game know, at least on some level, to what extent the Old Firm rivalry matters. It’s up there with El Clasico as something of a footballing outlier. Almost every football fan, regardless of their nationality or allegiance, watches El Clasico. It’s this way with matches between Celtic and Rangers too. Well, it certainly used to be. Throughout the 1990s and into the early 2000s, the Old Firm rivalry was just as big as anything the Premier League could offer up. It wasn’t just the rivalry that drew the eye, but the stars too - Henrik Larsson, Paul Gascoigne, Lubo Moravcik, Brian Laudrup. In every possible way, it was a match that carried great significance. The stars no longer shine so brightly in Glasgow, though. That isn’t to say that Celtic and Rangers don’t boast quality, because they do. In Olivier Ntcham, Odsonne Edouard, Kieran Tierney and Callum McGregor, the Hoops possess more than a few standout performers. Rangers could say the same of Alfredo Morelos, Scott Arfield and Allan McGregor. Both teams also made the group stages of the Europa League this season, with Celtic progressing to the last 32.