Juan Martin del Potro def. Roger Federer – 2009 US Open:
Federer was simply on fire heading into the 2009 US Open. So much so, in fact, that he was gunning for his sixth consecutive win.
But the No. 6-seeded del Potro took him to the limit, eventually outlasting Federer in the fifth and final set to complete the historic upset. The loss marked a decided down period for Federer, who seemingly couldn’t rekindle his previous magic after this defeat.