With a whopping 38 league titles, nine European Cups and 19 FA Cups between them, you can probably guess that Liverpool and Manchester United have had some pretty good players on their books over the years.
So what would an XI of the best players from each of these clubs look like? Well, we've tried to work just that out.
GK - Ray Clemence (Liverpool)
The definitive number one of Liverpool's defining era.
Clemence was an unstoppable force for the entirety of the 1970s after breaking into the first-team at the start of the decade, and inspired Bill Shankly and Bob Paisley's teams to five league titles and three European Cups before losing his spot to Bruce Grobelaar in 1981.
He left for Tottenham and would go on to play 16 times against the Reds, but not one tarnished his reputation - either as a Liverpool legend or a formidable shot-stopper.
RB - Phil Neal (Liverpool)
Phil Neal ran so Trent Alexander-Arnold can sprint. The best right-back in Liverpool's history had the nickname 'Zico' for a reason.
Neal was as dependable as they come, but he was also a force to be reckoned with going forward. Two of his 59 goals for Liverpool came in European Cup finals, and he is the only player to have featured in each of the Reds' four cup wins in the 1970s and 80s.
CB - Rio Ferdinand (Manchester United)
Now best known for hilariously jumping the gun when United appointed Ole Gunnar Solskjaer, there was a time, not too long ago, when Ferdinand was more than a clumsy pundit; he was one of the most feared central defenders in the Premier League.
He was twice English football's record transfer; in 2000, when he moved to Leeds for £18m, and in 2002, when Manchester United splashed out £30m. As steep as that fee might have seemed, however, it proved to be a drop in the bucket compared to his contributions.
His fearsome presence at the heart of the United defence earned him six Premier League titles. He didn't need that boxing career anyway.
CB - Alan Hansen (Liverpool)
Turns out he was more than just a dour-faced Match of the Day pundit. A lot more.
Sauchie-born Hansen was one of the best signings in Liverpool's history. Arriving from Partick Thistle for £100,000 in 1977, the classy ball-playing defender was a central part of virtually everything that came their way in the 1980s.
Two of his 14 Liverpool goals came against Manchester United; in the 1979 FA Cup semi-final, and in a 2-0 league win later that year.
LB - Denis Irwin (Manchester United)
Denis Irwin shares a record with fellow Manchester United alumnus Roy Keane; with 19 career trophies, he is the joint most successful Irish footballer of all time.
Every single one of those; including a breathtaking seven Premier League titles between 1992-2001; came in a Manchester United shirt.
He was a decent left-back too.
RM - George Best (Manchester United)
Best was football's original celebrity; in 1966, he was nicknamed 'El Beatle' for the comparisons he drew with the Manchester rock and roll sensations.
On the pitch, though, he rarely let it get to his head. Best is renowned as one of the best players of all time, and one of the most technically gifted of his era.
Considering his era included Pele, that's a good effort.
CM - Steven Gerrard (Liverpool)
The fact he never won a Premier League title is often used as a slight against Gerrard, and while it is a pretty major black mark against his name, it's telling that despite his lack of league success, the former Liverpool captain remains in any conversation regarding the greatest midfielders of the modern era.
He almost single-handedly dragged Liverpool back from the dead in the 2005 European Cup final in Istanbul, while his display in the 2006 FA Cup final against West Ham - which Liverpool won on penalties after a 3-3 draw - was so good that it has been monikeredThe Gerrard Final.
CM - Bobby Charlton (Manchester United)
Before the Sir Alex Ferguson era at United, there was the Bobby Charlton era. It was far less illustrious; yielding 'just' three league titles in his 17 years as a player.
But while he was never part of a hugely successful dynasty like those who would come decades later, the legendary England captain remains thought of as one of the greatest ever.
He was the first ever British player to win Ballon d'Or.
LM - Ryan Giggs (Manchester United)
You could make a case that no player has ever served a club quite as well as the skilful and clinically precise Giggs served Manchester United. He spent his entire professional career - all 24 seasons of it - at Old Trafford, and he has made 200 more appearances for the club than any other player, at 963.
His service didn't stop there either - he stepped in as interim manager after David Moyes was sacked, and he now manages Wales.
ST - Kenny Dalglish (Liverpool)
Ole Gunnar Solskjaer, Robbie Fowler, Andy Cole, Luis Suarez, Dennis Law, Fernando Torres, Ruud van Nistelrooy; choosing the strikers for this team was like picking your favourite puppy from a litter.
King Kenny, though? Never in any trouble.
You could make a strong case for the Scot as the best player to ever feature for either club, and given they have won 38 league titles and nine European Cups between them, that is quite something.
Dalglish's reputation was only furthered by his service to the club as manager in the wake of the Hillsbrough disaster - a true legend.
ST - Wayne Rooney (Manchester United)
Rounding the team out with a misunderstood modern great, Rooney will perhaps never get the credit he deserves, given he was far from the sexiest forward of his generation, but there can be no denying he was one of the most effective.
His work-rate was - and still is - tireless, and on 253 goals, he remains the club's record goalscorer. Given that Cristiano Ronaldo is the only active player with more than 100, that may well be a record that is never broken.
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