#3 Juan Martin del Potro (2009)
Roger Federer, the five-time defending champion on a record 40-match win streak at the tournament, arrived at a sixth consecutive US Open final where he faced 20-year-old Juan Martin del Potro.
Playing in his 4th Major final of the year, the 15-time Grand Slam champion was faster off the blocks as he took the opening set 6-3. Serving for a two-set lead at 5-4, Federer arrived at 30-0. A contentious video referral at 30-30 robbed the Swiss of a set point as Del Potro fired consecutive forehand winners to break back and take the set in a tie-break.
For the first time in the match, the serene Federer appeared ruffled by the young Argentinian's onslaught but the Swiss re-focussed on the task at hand. Federer won three games in a row from 3-4 down as Del Potro leaked successive double faults to concede a two-sets-to-one lead.
At 5-4, 30-30 on the Argentinian's serve in the fourth set, Federer was two points away from an Open Era record sixth US Open title but Del Potro slammed the door shut and won the ensuing tie-break to force a decider.
Federer ran out of steam in the fifth as Del Potro fired blistering forehand winners, breaking the Swiss twice to win the biggest match of his career and land a maiden Grand Slam title.
With his maiden Slam at Flushing Meadows, Del Potro became the youngest US Open champion in 18 years since Lleyton Hewitt triumphed in 2001.