WHAT HAPPENED: Juan Martin del Potro, the 2009 US Open champion who in the intevening years had four wrist surgeries that displaced him from the top of the men's game, ensured that yet again there would be no meeting of Rafael Nadal and Roger Federer in New York.
Delpo backed up his remarkable, come-from-behind fourth-round victory over Austrian Dominic Thiem and defeated the No. 3 seed Federer, 7-6, 3-6, 7-6, 6-4 - the same Swiss whom long ago the Argentine upset in that memorable '09 final.
Now it is the tall and popular del Potro, rather than "The Maestro," who advances to meet the top-seeded Nadal in the semifinal on Friday.
Del Potro survived an improbable and crucial third-set tiebreak, including four set points on Roger Federer's racquet, to win in two hours and 50 minutes.
The Argentine employed his brand of power tennis, including biggest and best weapons - his massive serve and imposing forehand - to thwart Federer.
"I played my best match of the tournament," said del Potro.
"I think it's my home court, too," he added, speaking of Ashe Stadium.
The 59-minute third set, and especially the tiebreak, was the turning point. Federer had rebounded from a 0-3 deficit early in the set. In the tiebreak, the powerful Argentine trailed continually until finally securing a 9-8 advantage by ripping a stunning cross-court forehand winner.
In the fourth and final set, del Potro surrendered only three points on serve and committed just one unforced error.
Federer vs. Del Potro
WHAT IT MEANS: Del Potro, seeded just 28th, is into his third career major semifinal. Throughout the match, Arthur Ashe Stadium reverberated with the Argentine soccer chants of "Ole, Ole, Ole, Ole, Delpo, Delpo!" that swirled down from the upper decks and reverberated off of the roof.
The Spaniard Nadal and his great rival Federer have met in every Grand Slam the US Open.
MATCH POINT: Del Potro certainly has momentum. Can he parlay his role as super spoiler into an upset of Nadal? Their head-to-head gives only a slight advantage to Rafa, eight matches won to five for del Potro. Del Potro won the last two meetings, both on hardcourts. But perhaps even more important, in that 2009 run to the US Open championship, del Potro crushed Nadal in the semifinal, 6-2, 6-2, 6-2.