David de Gea
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It took Manchester United six years to find an adequate replacement for Peter Schmeichel in the shape of Edwin van der Sar, and Sir Alex Ferguson learnt from that mistake by drafting in David de Gea ready for Van der Sar's retirement in 2011.
De Gea's first season in England was not without its troubles - he was even dropped in favour of Anders Lindegaard at spells throughout the campaign - but he has since developed into one of the best goalkeepers in world football.
The Spaniard was close to leaving the club for Real Madrid in 2015, but an admin error scuppered the deal and he quickly resumed his spot in goal at United, pulling off a string of remarkable saves season after season.
At the time of writing De Gea has 200 Premier League appearances to his name from his six years at Old Trafford, during which time he has won one Premier League title, the FA Cup, the League Cup and the Europa League.
A four-time member of the PFA Team of the Year, De Gea was also named Manchester United's Player of the Year three seasons in a row from 2013 to 2016.