To fans of neither, few clubs elicit such dislike as Manchester United and Real Madrid.
Both serial winners; on a cosmetic level at least, it is generally assumed that downturns in form or performances are to be applauded.
Yet, in human terms, the 60th anniversary of the Munich air disaster today united all football fans in a general sense of grief for what was a tragic loss of life.
For Manchester United's footballing hopes, losing so many key, young members of a hugely successful squad set the club back tremendously.
However, with the hard work of those like Matt Busby, Jimmy Murphy and more, the club was driven on through sheer will power. That ten years later they would fulfill Busby's long-stated ambition of claiming the European Cup, simply beggars belief.
Documenting a time shortly after the accident, The Telegraph today detailed the efforts of John Ludden in his identification of the role Real Madrid played in helping United in such a dire hour of need.
Although the Spanish giants would set up a series of profitable friendlies with United, and raise funds selling commemorative pennants in Madrid, it was another offer made by the club that is surely the most interesting of all - in a football sense, certainly.
In an attempt to prop up United's understandably light squad, Real offered the club the use of Alfredo di Stefano for the remainder of the season.
A player subsequently described as the greatest he has ever seen by Bobby Charlton, Di Stéfano was at that stage a key component in Madrid's back-to-back winning European Cup side.
Ultimately bringing that number to 3 in the ill-fated 1957/58 season, the man from Buenos Aires, that would intriguingly play for Argentina, Colombia and Spain internationally, established himself as one of Real's outstanding players.
Unfortunately, the proposed loan deal was knocked back by the English FA, despite Di Stéfano's own enthusiasm at the prospect:
When United put the proposal to the Football League, it was knocked back, according to Ludden. Alan Hardaker, the Football League secretary, was no stranger to United.
Busby had fought with him over his refusal to permit United entry to the European Cup and now the obstinate Yorkshireman stood in their way again, reputedly arguing that the arrival of Di Stefano would block a place that could be taken by a British player.
A shocking lack of foresight from the Football League secretary, the prospect of seeing a player of Di Stéfano's apparent quality can only have served to lift the spirits of a city shocked by unimaginable grief.