Modern-day tennis fans have got used to there being consistent Grand Slam champions across all four tournaments. For about the past 10 years the ultimate winner has either been Roger Federer, Rafael Nadal and more recently Novak Djokovic or Andy Murray.

This has not always been the case, but when you get some of the best players to ever have played the game reaching the top of their abilities at similar times it is very hard for others to win titles. However, on this day in 2009, a young Argentinian stunned the previously unbeatable Roger Federer at the US Open.

Although the Federer of 2013 has failed to reach the quarter-finals in two consecutive Grand Slams, in 2009 he had a 40-match winning streak at the US Open which stretched back to 2003 and no-one realistically expected any player, not even Rafael Nadal, to beat him at Flushing Meadows. He had won the tournament the last five times and was still incredibly hungry for more success.

Enter the young pretender. By this point Del Potro was hardly unheard of, but no-one was talking about him as a potential champion at the US Open - just yet. He had shown signs of his promise earlier in the year at the French Open when he reached the semi-finals - his first - and came up against the Swiss. He was twice ahead but Federer in the end was just too strong and came through in five. Del Po would get another chance that year.

At Wimbledon, the Argentine's known weakest tournament, Del Potro went out in the second round to Lleyton Hewitt. However, he responded at the US and looked in fine form. He dispatched compatriot Juan Monaco in straight sets in the opening round on day two and did not take much longer to get past Jurgen Melzer either.

He lost his first set of the tournament to Austrian Daniel Kollerer in the third round before breezing past Juan Carlos Ferrero and making surprisingly light work of Marin Cilic in the quarters. If people were not yet discussing Del Potro as a potential winner of the tournament they were when he blew away none other than Rafael Nadal 6-2 6-2 6-2 in the semis to set up his second big date with Federer of the year.

It was the Argentine's first Slam final, so nerves were understandable. A sluggish start meant that he was a set and a break down very quickly, with Federer serving for the second at 5-4. Few punters would have been brave - or indeed stupid - enough to back Del Potro from this point. However, he has shown in his years on the circuit so far that he is a battler and he clawed it back to a tie-breaker before winning that 7-5.

Federer responded as only he could and took the third, with Del Potro then winning the fourth on another breaker. Now it was anyone's game and the momentum was with the Argentine. With Federer rattled and now playing into Del Po's strengths, the final set went 6-2 to the Argentine and the Swiss - along with all his fans - were stunned.

His triumph in 2009 remains Del Potro's only Slam to date, with injuries and drops in form meaning he has never quite hit the heights he did that year. All it would take, however, would be another fortnight like the one in September 2009.