Rafael Nadal and Roger Federer are on the verge of a third consecutive Grand Slam title showdown but the world's other two top tennis players are intent on changing the plot for the US Open final.
Four-time defending champion Federer will face Australian Open winner Novak Djokovic and world number one Nadal, the Wimbledon and French Open champion, will face British sixth seed Andy Murray in semi-finals set for Saturday.
Heavy rain in the forecast could delay the drama, but whenever the Fab Four step on the court to decide the finalists in the year's last Grand Slam event, expect tension-filled confrontations setting the stage for a date with destiny.
Second seed Federer has to hope it's third-time lucky after losing his third consecutive French Open final to Nadal and seeing the Spaniard deny him a sixth Wimbledon title in a row in one of the greatest matches ever played.
Federer enters his record 18th consecutive Slam semi-final, a rematch of his 2007 US Open final triumph over Djokovic, on a 33-match US Open win streak. Bill Tilden's run of 42 from 1920 to 1926 is the only longer men's streak.
The 27-year-old Swiss superstar has won 12 Grand Slam singles crowns, two shy of matching the all-time record of Pete Sampras, but this could be the first year since 2002 that Federer does not win at least one.
That's due to the emergence of Nadal, who captured Olympic gold last month at Beijing and has shown himself to be far more than a clay-court magician by breaking through to dethrone Federer at Wimbledon to reach the ranking pinnacle.
Nadal, 22, ended Federer's 237-week rankings reign last month and the left-hander will remain atop the ATP performance list no matter how the Flushing Meadows fortnight finishes.
A victory in the US Open final would put Nadal alongside Rod Laver, Pete Sampras and Federer as the only men to win three Slams in a row in the 40-year Open era.
"I'm here with very special motivation," Nadal said.
Nadal, who has won 19 Grand Slam matches in a row, could join Manuel Orantes as the only Spanish champions of this event in the Open era. Orantes won the US Open in 1975 when it was played on clay.
But title or not, Nadal has punctured the aura of invincibility that once surrounded Federer. This has been Federer's most difficult season since 2003.
The US Open offers a chance for Federer to reclaim a bit of the mystique or for Nadal to close his rival's last chapter and give himself a chance to win a fourth Slam in a row at next January's Australian Open.
"For (Federer) it's a big challenge now to win another Slam and stay in the race with Rafa to be number one at the end of the year," Djokovic said. "It's a bit strange to see No. 2 next to his name."
Then again, there are a couple of 21-year-old Europeans who would be just as happy if neither Federer nor Nadal make it to the trophy showdown at Arthur Ashe Stadium.
Serbian third seed Djokovic has lost six of eight meetings with Federer but beat him in this year's Australian Open semi-final on his way to taking his first Grand Slam title, beating France's Jo-Wilfried Tsonga in the title match.
Olympic bronze medallist Djokovic has reached his sixth Slam semi-final after reach his first Slam final here a year ago. If he wins the US Open he will move past Federer into second in the world rankings.
Murray has made the breakthrough run of the four to reach his first Grand Slam semi-final, ensuring that he will jump to fourth in the next ATP rankings to match Tim Henman and Greg Rusedski as the highest-rated British man ever.
It will take another breakthrough, however, to book a trip to the finals. Murray has lost all five prior meetings with Nadal but earned his respect.
"He can win the title," Nadal said. "For sure it's his first Grand Slam semi-final but he has played very important matches. It's going to be nothing strange for him."
Since taking a two sets to one lead in a fourth-round match with Nadal at the 2007 Australian Open, Murray has been unable to take a set off the skilful Spaniard, losing 11 in a row, three of them in a June Wimbledon quarter-final.
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