VIDEO: Keylor Navas has some weird training techniques. Could you stop 160 km/hr tennis balls?

In one of the most amazing performances of the tournament, Costa Rica goalkeeper Keylor Navas held Greece to only a single goal over 120 minutes — despite being down a man for almost half that time. He then went on to stop Greece's final penalty kick to advance to the quarterfinals.

So, how does a 'keeper end up becoming his side's hero? 

Practice. Lots of practice.

And if you're Navas, you prepare for the odds being against you be taking on some outrageous challenges. 

Here he is trying to stop Spanish tennis pro Pablo Andujar from blasting tennis balls past him at speeds approaching 160 kilometers per hour.