World number one Federer will play for his sixth consecutive US Open title and record-stretching 16th career Grand Slam crown on Monday against Argentine sixth seed Juan Martin del Potro, who is 0-6 lifetime against Federer.
But the moment everyone will be talking about from Federer´s semi-final triumph will be the back-to-the-net, between-the-legs running forehand which the Swiss superstar swatted past the stunned Serbian for an astounding winner.
"I do (practice) them a lot actually but they never work," Federer said. "That´s why I guess it was the greatest shot I ever hit in my life."
Viewing a television replay moments after the match, Federer exclaimed, "That´s unbelievable."
Djokovic was serving at 0-30 and lured Federer to the net, then lofted a lob to the back line that sent Federer dashing to run it down.
With no chance to spin, look back or otherwise set himself, Federer leaped above the ball, brought his right hand down the middle of his body and smacked the ball between his legs, just over the net and into the empty part of the court.
"I was in a difficult position. I had nothing to lose," Federer said.
The crowd roared its approval and Federer won with a forehand winner on the next point to end it after two hours 34 minutes.
"In these moments he comes up with some great shots," Djokovic said. "That shot. You heard the crowd. What can you say? You say well done. Too good. What can you do?"
Rising to the moment with an astounding combination of skill, luck and success convinced Federer that it w1as his best shot.
"Even though it´s like the third or fourth time I´ve hit it in a match now, the way I was able to hit it, with pace and accuracy, it´s something that happens so rare," Federer said.
"It was a semi-final of a Grand Slam after all. So to come up with that, to get match point against Djokovic here in the semis is amazing and that´s probably why."
Djokovic was broken only in the last games of the second and third sets and lost the tie-break by dropping five of the last six points.
Federer, in the semi-finals for a record 22nd Grand Slam event in a row, completed a career Grand Slam by winning the French Open crown in June and set a record with his 15th career Slam title in July at Wimbledon.
Djokovic was denied a third career Slam final after his 2007 US Open final loss to Federer and his 2008 Australian Open title run. Federer, 28, also beat Djokovic, 22, in last year´s US Open semi-finals.
The rain-delayed final marks the first time in 40 years that back-to-back men´s titles will be decided on Monday, Federer having captured last year´s final over Britain´s Andy Murray a day later than usual thanks to rain.
Federer, 9-4 all-time against Djokovic will make a 21st Slam finals appearance and his 17th in the past 18 Slams, missing out only at the 2008 Australian Open, when he lost to the speedy Serbian in the semi-finals.
Earlier, Del Porto, the giant sixth seed, was simply too powerful for the Spanish third seed, who was powerless to match the big-hitting coming at him from the other side of the net as his bid to win the US Open for the first time bit the dust.
"This is the best moment of my life," he said. "I was so focused every moment because Rafa is a great player and can run for five or six hours. I am not that strong, but I did my best and I am in the final."
Nadal, who endured his worst defeat in a Grand Slam tournament, said that he had been playing well early in the year before running into injury problems with his knees and then a stomach muscle strain.
"I had problems with serve and then to deal with a player like this, playing unbelievable tennis," he said.
Nadal, in only his second US Open semi-final, was out to become just the seventh player to complete a career Grand Slam of the four major titles having already won the French Open four times and Wimbledon and the Australian Open once each.
The 23-year-old from the Mediterranan island of Mallorca was in line to follow Fred Perry, Don Budge, Rod Laver, Roy Emerson, Andre Agassi and Federer, who completed the set at the French Open in June.
Del Potro, who turns 21 on September 23, was aiming to become the first South American US Open finalist since Guillermo Vilas won the title in 1977.
Both players had early break chances in a tightly-contested start to a match delayed by 24 hours because of heavy rain on Friday and Saturday.
But it was outsider Del Potro who struck first in the fourth game, unleashing a big forehand to get to break point and then forcing Nadal into hitting long on a backhand volley at the net.
There were no early signs of discomfort from Nadal from the stomach muscle strain that hampered him in earlier rounds, but he was simply being outhit by the giant South American who held easily to take a 4-1 lead.
Del Potro went into the match as the only player to defeat Nadal twice during the year, winning their last two matches in Miami and Montreal, both on hardcourts.
He continued that recent domination by breaking Nadal for a second time to take the first set, doing most of the damage with his big forehand, hit flat to either flank.
Nadal´s problems worsened at the start of the second set as he started to look in some pain again from the abdominal injury and he promptly dropped serve again with a double fault on break point as Del Potro took a 3-1 lead.
The Argentinian staved off a fifth straight break point in the following game to lead 4-1 as Nadal looked anxiously towards coach Uncle Toni in the players´ box.
Nadal was unable to stay the pace with the bigger man and he looked lost for answers as Del Potro broke once again to take the second set.
Del Potro held serve to open the third set and he pounced again in the following game, blasting Nadal´s serves back with ease to break for the fifth time in the match.
The Argentinian eased to a 5-2 lead and then broke the Nadal serve to love to roar into the championship match.
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