Ruben Dias completely transformed Manchester City's form last season after sealing a £64million move from Benfica, showing leadership and defensive nous in abundance to lead Pep Guardiola's men to reclaiming the Premier League title.
The Portuguese defender deservedly won end-of-season awards to vindicate the rave reviews he had received throughout the season, winning both Premier League Player of the Season and the Football Writers' Association Player of the Year.
A new six-year City contract followed in the summer and having been hailed as having a similar impact at the Etihad Stadium to Virgil van Dijk at Liverpool, Jose Mourinho was left in no doubt as to how vital Dias had been for Guardiola's side.
Ruben Dias won the Football Writers' Association Player of the Year award last season
He transformed Manchester City's defence to help the club win their third title in four years
'Ruben Dias is the best centre back in the world now,' he told The Sun shortly after being appointed Roma boss. But it appears now that not everyone is in agreement.
Rio Ferdinand believes Antonio Rudiger is the new best centre back in the Premier League ahead of the Portugal and Holland internationals, with the German having become an influential figure in Thomas Tuchel's side.
Rudiger struggled for game time under Frank Lampard and faced an uncertain future at the club as a result, but has bounced back since Tuchel's appointment for the European champions, who are now desperate to tie him down to a new deal.
Dias and Rudiger will now face each other trying to keep the ball out of their nets when the English champions travel to the Champions League holders in Saturday's early kick-off.
But who do the statistics say would have bragging rights in their own individual battle? Sportsmail looks at the numbers to see who comes out on top.
Rio Ferdinand (R) believes Chelsea's Antonio Rudiger (L) is now the best in the business
Manchester City conceded five goals against a Jamie Vardy-inspired Leicester City in their final game before announcing Dias as a shiny new signing.
The 24-year-old subsequently galvanised a team that was struggling defensively and added the steel - imbued with the more technical side of the game his team-mates have come to master over the years - which was necessary to wrestle the title off Liverpool.
Guardiola's men were also able to win their third Premier League title in four years after conceding just 32 goals last term, unsurprisingly the least of any side.
Chelsea were their closest competitors when it came to the goals conceded column, letting in 36 goals, but they were made to wait until the final day to scrape fourth spot.
But the Blues may well have beaten City in that regard had Dias not arrived at the Etihad Stadium to patch up and reinforce a defensive line that looked vulnerable at times when the likes of Eric Garcia and Nathan Ake were at its heart.
No City player managed to match or better the Portugal international's 23 blocks in 2020-21
Rudiger (centre) has been part of a side that has managed 21 shutouts under Thomas Tuchel
City kept a clean sheet in exactly half of Dias' 50 appearances in all competitions in 2020-21, and conceded just one goal every other game on average across the entire campaign with him commanding proceedings at the back.
No City player managed to match or better his 23 blocks or 49 aerial clearances, and he combined that with calmness on the ball as well as an effective passing range, a quality perhaps equally as crucial in a side managed by Guardiola.
But after their London derby victory at Tottenham last weekend, it is now Chelsea's turn to receive envious looks from the rest of the league - and Europe for that matter - when it comes to their defensive record.
Another shutout at the Tottenham Hotspur Stadium means the Blues have now kept more top-flight clean sheets (15) than they have conceded Premier League goals (14) since Tuchel took charge.
Former Manchester United defender Ferdinand claims Rudiger has had an 'immense' impact on that return for European champions, but does it surpass the effect Dias has had during his time in English football?
Rudiger had a superior tackle ratio to Dias last season, winning 23 of his 31 tackles
Well, as Ferdinand predicted, there is very little to split the duo when it comes to their numbers in defence, but the statistics imply that even last season, the German may just have had the edge.
Firstly, it must be said statistics
