In the history of world football, only 15 defenders have ever been sold for more than €50 million (£46m/$59m).
On seven of those occasions, Manchester City have been the buying club. Among the other eight occasions, only Manchester United have ever forked out as much to bolster their backline more than once.
It highlights the struggles Pep Guardiola has faced when putting together a defence to match the mesmeric attack he has arranged at the Etihad Stadium.
The latest to arrive is Ruben Dias, with City having paid Benfica an initial £62m ($79m) for the centre-back, with the potential for a further £3.3m ($4.2m) in add-ons.
The Portugal international’s signing ends City’s 18-month search to replace former captain Vincent Kompany, with Dias set to be thrust straight into the action as Guardiola attempts to tighten up a backline that was brutally exposed during Sunday’s humiliating loss at home to Leicester City.
However, merely signing one of the most expensive defenders in the world is no guarantee of stability, as City know all too well.
Among their six previous €50m-plus defensive signings, there have been some successes.
Despite being uncapped by France, Aymeric Laporte has become the leader at the heart of City’s defence and he missed the visit of Jamie Vardy & Co. as he looks to regain full match fitness following a positive Covid-19 test in pre-season.
Kyle Walker, meanwhile, has also made a huge contribution since his move from Tottenham, playing a major role in City’s two title triumphs under Guardiola.
But there have been more misses than hits.
Eliaquim Mangala was a club-record signing when he arrived for €51.7m (£41m/$69m) from Porto in the summer of 2014, but he flopped spectacularly in the Premier League.
The France international never recovered from scoring an own goal and conceding a penalty in his first away game, at Hull City, and made just 59 Premier League appearances in five years before leaving on a free transfer to Valencia.
Meanwhile, the other three €50m-plus signings – John Stones, Benjamin Mendy and Joao Cancelo – remain at the club but are all fighting for their City futures after struggling for fitness and consistency under Guardiola.
Dias completes the less-than sensational seven, but there are reasons to suggest he will be a good fit.
City have been lacking a defensive leader since Kompany’s departure and it is believed that Dias, who captained Benfica at Under-17 and U19 level, will bring strength and confidence to his new role.
He is also better skilled in the ‘darker arts’ of defending than Guardiola’s current options, and though the ex-Barcelona boss denies such scrupulous acts are part of his strategy, having a more streetwise centre-back is advantageous.
Stopping threatening attacks before they get too dangerous is an important part of Guardiola’s defensive game plan, though his players have failed to carry it out in recent months.
Guardiola’s instructions are why Fernandinho and Rodri are regularly accused of tactical fouls and why Ederson is the most advanced goalkeeper in the world, coming a long way from his penalty area to stop goal threats rather than staying back to make saves.
Stones and academy graduate Eric Garcia, however, can be far too honest in their defending, with the Spanish teenager having been made to look particularly naive against Leicester by the cunning Vardy.
Dias is far more accustomed to the odd nudge, pull or even foul and sensible yellow card where required to stop an attack before it starts.
That is important because Guardiola is not about to change the high defensive line he has used throughout his managerial career, meaning he needs players that can cope with playing in such a risky manner.
Leicester, like others before them, utilised a low block to crowd out City’s own offensive threat before breaking at pace to puncture a fragile backline. Dias needs to bring solidity to a defence that has grown increasingly susceptible to swift counterattacks.
But Dias won’t just help out at the back. Guardiola’s centre-halves are also required to make a contribution to City’s own goal tally and Dias will add an aerial threat from set-pieces, having scored 12 goals in slightly over three seasons for Benfica – which is more than Laporte, Stones and Garcia combined.
The aspect of Dias’ game that will be most closely scrutinised, of course, is his use of the ball.
Quickly changing the point of attack to wide areas with long passes is an essential part of the centre-back’s role under Guardiola, and it is an attribute that those who have tracked Dias’ career to date suggest that he may need to improve upon.
The pressure will be on Dias from the moment he makes his City debut, though few defenders to have arrived from the Primeira Liga have found adjusting to life in the Premier League easy.
Mangala and Nicolas Otamendi earned their reputations at Porto but for the most part struggled at City, while Manchester United’s Marco Rojo, Diogo Dalot and Victor Lindelof were all acquired from top-flight Portuguese clubs before going on to underwhelm at Old Trafford.
David Luiz, who left Benfica for Chelsea in 2011, has also had a lot of tough times in England, both with the Blues and current employers Arsenal, with only ex-Chelsea centre back Ricardo Carvalho proving an undoubted success, after arriving from Porto in 2004.
Dias, then, has it all to do. History is against him. Not only have many former Primeira Liga players struggled in England, the majority of the defenders that City have signed at a combined cost of £400m ($514m) since their Abu Dhabi-led takeover have proven a waste of money.
Surely they can’t get it wrong again, though, can they?..