Squad depth is the key to success in football, especially in the upper echelons of the professional game.
Your preferred starting XI can be the best on the planet, but if you haven't got quality waiting in reserve, injuries and lack of competition will soon derail any hopeful season.
Strength in numbers is the main reason why the Premier League's established top six are usually the top dogs in the division.
So with that in mind, we've decided to take a look at all six team's current squad depth for the 2020/21 season and ranked them accordingly.
Given we've provided just one back-up in each of the 11 positions - so 22 players maximum - a few squad players have failed to make the cut entirely.
6. Man Utd
Anthony Martial, Marcus Rashford, Mason Greenwood, Bruno Fernandes and Paul Pogba are an attack-minded quintet up there with the best in the world.
But four of the positions mentioned lack quality cover, with Donny van de Beek the exception and the Dutchman's versatility will be sorely needed for the Red Devils to stand a chance of rotating effectively.
In defence, the depth is pretty shocking as well and the fact Phil Jones is still a member of the squad says it all. Dean Henderson and David De Gea competing for the number one spot is the club's only saving grace in the pragmatic positions.
It's simple, United's current squad cannot challenge for the title and their talented starters are too heavily relied upon for what will be a hectic 2020/21 season.
Arsenal just edge ahead of United thanks to the fact they have far more in reserve going forward.
Nicolas Pepe, Gabriel Martinelli and Eddie Nketiah are three very exciting options to fill in for the usual big hitters, while the Gunners do have strength in numbers at the back these days as well.
Bukayo Saka's ability to slot in both at the back and operate in various attacking roles only adds to Arsenal's depth for the 2020/21 season.
On paper, it's not a squad the screams 'title challengers', but it certainly has the potential to break into the Champions League places.
Jose Mourinho always seems to be complaining about the lack of squad depth available to him at Tottenham, but we think it's pretty darn good.
Gareth Bale's addition to the team should reduce the goal scoring burden on Harry Kane's shoulders, with Steven Bergwijn and Erik Lamela providing quality depth out wide.
The midfield and defence don't look bad either, especially after the additions of Pierre-Emile Hojbjerg, Matt Doherty and Sergio Reguilon this summer.
If this Spurs squad can finally click under Mourinho, the north London outfit are going to be a serious problem in 2020/21.
When Hakim Ziyech, Christian Pulisic, Ben Chilwell and Edouard Mendy are all settled, fit and firing, Chelsea are going to be a huge threat.
Academy products Callum Hudson-Odoi, Mason Mount, Ruben Loftus-Cheek and Tammy Abraham will provide stellar cover in the forward roles within Frank Lampard's favoured 4-2-3-1 setup.
Chilwell and Mendy's additions at the back will likely transform the Blues' defence in 2020/21. Cesar Azpilicueta, Kurt Zouma and Fikayo Tomori aren't bad options to have in reserve either.
The weakest area depth-wise is in midfield and it's no wonder the Blues are eager to sign West Ham's Declan Rice. But overall, a very strong squad, which is what you expect after a summer of lavish spending.
2. Man City
City's depth in attacking areas is easily the best in the top six and despite their back-line looking suspect, Pep Guardiola really does have a wealth of options at his disposal in defence - Ruben Dias will also join the party when his move is made official.
But it's in midfield where City's squad is stretched pretty thin and that's why they miss out on top spot for us.
Ilkay Gundogan will have to act as back up for both Rodri and Fernandinho during the 2020/21 season, unless Guardiola is prepared to utilise Oleksandr Zinchenko in one of the deep midfield roles.
Don't bet against City splashing the cash to strengthen their midfield in the final week of the transfer window, though...
The undisputed number one. Liverpool's second XI would probably challenge for the top four, that's how impressive the club's recruitment has been.
Centre-back is the only area of concern and natural options are so sparse that we've had to include teenager Rhys Williams as back up to Joe Gomez.
But in reality, Fabinho can fill in for either Gomez or Virgil van Dijk, with the Brazilian excelling as a centre-back in the 2-0 win away at Chelsea.
Liverpool's squad is so stacked that we've had to leave out Curtis Jones, Divock Origi, Harvey Elliot and Rhian Brewster - scary times for the rest of the Premier League!
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