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It seems something of a paradox that Manchester City now possess three of the four most expensive defenders in football history following the capture of right-back Kyle Walker from Tottenham Hotspur.
City have been spending big on defenders for years, but they look no closer to becoming the strong defensive unit that the transfer fees suggest they should be.
There remains some uncertainty over the exact fee that City paid for Walker, with one side suggesting a deal worth up to £53 million and the other insisting it was no more than £50m, but it's a matter of loose change considering that the England full-back is now either the game's costliest-ever defender or merely the joint-record holder with David Luiz, who cost Paris Saint-Germain £50m when he left Chelsea in 2014.
John Stones, at £47.5m, is next, followed by Eliaquim Mangala, City's forgotten (and unwanted) man, who cost £42m when he arrived from FC Porto in 2015.
By the time City complete a deal for Monaco left-back Benjamin Mendy, who is likely to command a fee in excess of £40m, Pep Guardiola will be able to count on four of the top five in the world's most-expensive defender list.
Nicolas Otamendi, at £31.5m, is not far behind Arsenal's Shkodran Mustafi (£35m) and PSG's Thiago Silva (£33m) in the top 10, so on the face of it, Guardiola has an array of high-end players to choose from when it comes to keeping the ball out of the City net.
The unfortunate reality for Guardiola, however, is that his best defender remains an injury-ravaged centre-back who cost a mere £6m when arriving from Hamburg in August 2008. Vincent Kompany, the City captain, is the perfect example that a price tag does not automatically define a player's value to a team.