6. Thibaut Courtois
You have to be a pretty good goalkeeper to crack the top 10 - keepers don't usually start, let alone reach anywhere close to peak performance level before age 28 - but Courtois is the exception.
That's because he is exceptional. Mid-way through his third year as a starter at Atletico Madrid, reports claim he's returning to Stamford Bridge after the World Cup with Petr Cech in his sights.
Now, Cech is a world-class keeper. But it's testament to his ability that few would be surprised if the Blues opted for the 21-year-old Belgian.