The four underdogs who have won Grand Slams in the last decade

#3 Juan Martin del Potro - 2009 US Open

Del Potro would beat Roger Federer for the 2009 US Open title

Juan Martin del Potro has been a thorn in the side of the Big Four for a long time. Though he has an inferior career record against all of them (14-39), he still seems to find a way to win when it matters the most.

Del Potro denied Djokovic an Olympic medal at the 2012 games by winning their bronze medal clash. He beat Federer in consecutive years to win the maestro’s home Swiss Indoors title, and had his Major breakthrough even before Andy Murray had captured a single Grand Slam title.

The Argentine's greatest triumph came at the 2009 US Open, where the sixth seed became the first player to beat Rafael Nadal and Roger Federer in the same major tournament en route to the title.

After a brave comeback against Marin Cilic in the quarters, Del Potro flattened Nadal in a crushing 6-2, 6-2, 6-2 defeat. He would unexpectedly go on to hound Federer again in the final, coming back from a set and a break down to triumph in five sets.

Del Potro became the first Argentine since Gaston Gaudio in 2003 to win a Grand Slam, and would rise to number 4 in the rankings. He continued his success by beating Federer again at the season ending ATP Tour Finals where he would finish runner up to Nikolay Davydenko.