When Jose Mourinho arrived at Chelsea in 2004 he quickly identified the problems within his squad.
He saw that the spine of his team, those playing in key positions through the centre of the pitch, had to be improved.
Mourinho quickly dived into the transfer market and bought Didier Drogba, Ricardo Carvalho and Petr Cech in his first summer at Stamford Bridge.
Gary Neville spoke this week about how Manchester United's side has a weak spine
Man United trio Harry Maguire, Marcus Rashford and Paul Pogba in action this season
With Frank Lampard, John Terry and Claude Makelele already in position, he now had a group that could dominate English football for years.
Earlier this week, Gary Neville said Manchester United do not have those players in those key areas.
He highlighted that last week's team against Leicester had a blend of youngsters still finding their feet at the top level and a group of experienced players whose best days are behind them.
Speaking on Monday Night Football, Neville identified Liverpool trio Virgil van Dijk, Alisson and Fabinho as signings by Jurgen Klopp that have turned the Reds into genuine title contenders and challenged Ole Gunnar Solskjaer to find similar players.
Statistics show he is right too. With Alisson, Van Dijk, Fabinho and Roberto Firmino on the pitch at the same time since the start of the 2018-19 Premier League season, Liverpool have won 76.9 per cent of their matches.
They have 20 wins from 26 games, losing just one, and have scored 60 goals and conceded just 17.
Two key Liverpool players - Virgil van Dijk (left) and Fabinho (right) - working in tandem
Roberto Firmino is often at the top end of Liverpool's spine, which has an excellent record
Liverpool's record with their spine of Alisson, Van Dijk, Fabinho and Firmino since August 2018
Manchester City's central quartet is even stronger. With Ederson, Aymeric Laporte, Fernandinho and Sergio Aguero in tandem, Guardiola's side have amassed a ridiculous win ratio of 88 per cent.
They have won 22 of 25 matches when they have played together, finding the back of the net 72 times and letting in a mere 10 goals.
It is not just collectively that Liverpool and City stand out above their rivals though. The players in their spines are regular producing better individual performances than their closest rivals too.
Since August 2018, Ederson (22) and Alisson (21) have kept significantly more clean sheets than their fellow No 1s and their minutes per goal conceded ratio is close to double that of David de Gea and Bernd Leno.
Manchester City goalkeeper Ederson (left) and defender Aymeric Laporte in action
How the top six goalkeepers compare since the beginning of last season
A comparison of some of the prominent defenders at the Premier League top six clubs
In defence, Van Dijk has a tackle success rate of 71.43 per cent while Victor Lindelof is just above 60 per cent. Laporte's passing accuracy (92.41 per cent) towers above his contemporaries.
Fabinho and Fernandinho may be Brazilian but their work at the base of midfield is far from what we are accustomed to seeing from South American players.
They are both at the top of the list for duel success, while Fernandinho's tackle success (75.44 per cent) is far superior to the rest.
City's midfield powerhouse Fernandinho in action during their recent win over Brighton
Fernandinho's tackle success percentage stands out in a comparison of top six midfielders
Manchester City's record with their spine of Ederson, Laporte, Fernandinho and Aguero
Both teams place as much importance on defensive stability as they do on attack and Firmino has proven to be the man to get the best out of Sadio Mane and