Way back before the Premier League even existed, football tactics were little more than selecting your side's best 11 players then sending them out on a Saturday to play football.
Squads were thin – indeed in the 1980-81 season Aston Villa used only fourteen players all season in winning the title. These days you need 18 players just to start an top-flight match.
A decent Premier League squad now consists of enough players to fulfil every possible eventuality two or three times over – and perhaps Manchester City (if you discount Chelsea's squad of 100 or so Under-23 players) have sent the concept of 'strength in depth' to new soaring heights.
Here we take a look at City's first, second and third-choice XIs, and ask would the second XI be good enough to qualify for Europe, and would the third XI survive in the top flight?
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Edinson; Walker, Otamendi, Kompany, Mendy; Fernandino, D Silva, De Bruyne, Sane, Mahrez; Aguero.
It says more about City's strength in depth if you consider who doesn't make it into the first XI rather than who does. Despite his excellent performances for England at the World Cup, John Stones has a fight on his hands to reclaim his place from Nicolas Otamendi, who had a brilliant 2017-18 campaign.
A few other players are also missing from our selection of City's 'first choice eleven' who would simply walk into most other top-flight sides – Fabian Delph, Bernardo Silva, Raheem Sterling and Ilkay Gundogan for example.
Pep Guardiola has carefully pieced together an exceptional squad and although some players – particularly Kevin De Bruyne – would definitely reduce the effectiveness of the team if lost via injury, there seems to always be someone 'nearly as good' ready to step in should someone else suffer a knock or need a rest.
Bravo; Danilo, Laporte, Stones, Mangala, Delph; Foden, Gundogan, B Silva, Sterling; Jesus.
While Sterling won't exactly be best pleased that he's now regarded as a second-choice selection after the signing of Riyad Mahrez (and it's going to be an interesting battle in the 2018-19 season to see which of the pair is selected the most often), the tricky English forward still forms part of a very talented 'Manchester City reserves' XI.
Not many sides can relegate talent such as Stones, Bernardo Silva, Sterling, Gundogan and Gabriel Jesus to their second string, but such is the depth that Guardiola has at his disposal, his second-choice side would still push for a Europa League place in the EPL at a minimum.
There's a youthful element to this selection too, with up-and-coming Citizens such as Aymeric Laporte (24) and Phil Foden (18) both included.
Bravo; Roberts, Sandler, Denayer, Adarabioyo; Garcia, Foden, Luiz (D), Diaz (B), Zinchenko; Nmecha.
This side is mainly made up of youngsters, some of whom will spend the campaign away from the Etihad Stadium to continue their development.
Even City fans may not have heard of some of the selections, but plenty of these names have big futures in the game. Watch out for the likes of Tosin Adarabioyo (20), Brahim Diaz (18) and Oleksandr Zinchenko (21), who is facing a make or break campaign.
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