The U.S. Open enters the final four on Saturday with top seeds Novak Djokovic and Roger Federer looking to see off younger rivals in the form of their life and set up their second straight Grand Slam final. After falling to a painful defeat at Wimbledon, Federer, aged 33, is again chasing Grand Slam No. 18, but must negotiate a meeting with Croatian Marin Cilic before getting a rematch with Djokovic, if the world No. 1 can get past marathon-man Kei Nishikori.

Federer will be breathing a huge sigh of relief that he has simply made it this far. In his quarterfinal under the lights on Thursday, the Swiss trailed two sets to love against a newly focused Gael Monfils and then faced two match points in the fourth set before fighting back to win 6-2 in the final set of a thriller. Monfils certainly provided a stern test, but there is no doubt that on paper Federer was handed a spot on the easier side of the draw. Roberto Bautista Agut is the highest seed Federer has faced at 17. His next opponent is seeded just three places higher and was ranked as low as 37 at the start of the year, but Federer is well aware that Cilic is not to be taken lightly.

“He's playing really nice, you know,” Federer said. “I must say he's really cleaned up his game. I mean, he's done well in the past. It's not like, you know, he's come from the top 50 player to all of a sudden knocking on the top 10 door. He's been there before. Let's be honest. But it just feels it's not so much in the other guy's racquet.”

Cilic has bounced back strongly from the real low last year of a drugs ban, which he still contests, for taking a banned stimulant. Now he is back in a Grand Slam semifinal, four years after seemingly marking himself out as one of the game’s next big things when reaching the last four of the Australian Open aged 21. After a grueling five-set win in stifling heat and humidity against Giles Simon in the fourth round, the Croatian upset sixth seed Tomas Berdych in straight sets on Thursday.

Like Federer, Djokovic was pushed hard in the quarterfinals. The Serbian faced a grueling three-and-a-half-hour battle with Andy Murray, but emerged strongly at the end to claim a four-set win and continue his fine performances at the 2014 U.S. Open. His form has quickly returned to a high level following a lull in the wake of his Wimbledon win and subsequent marriage. Djokovic was never in doubt that his best would return when it mattered.

“I was aiming to play my best tennis in U.S. Open, and I knew that's going to happen,” he said. “I mean, I was believing it's going to happen, and I'm really glad that I'm in another semifinal here, you know, tough draws, some tough players that I played against. Of course as the tournament progresses I'm trying to gather together as much confidence as I can.”

In contrast, Nishikori’s run to the U.S. Open semifinals, and particularly the manner of it, has surprised even himself. The 24-year-old came into the event on the back of another in a frustratingly long line of injuries, but has proved his fitness in extraordinary fashion with back-to-back five-set victories over Milos Raonic and Stan Wawrinka to become the first Japanese player to reach a major semifinal since 1933.

Predictions: Nishikori has played some superb tennis to get this far and bring together the improvements he has made under coach Michael Chang. And he may not be unduly hampered by his exertions in the last two rounds, having had the benefit of two days’ rest. But that is unlikely to be enough to oust the top seed. It won’t be straightforward for Djokovic, but he is playing too solidly right now and has the weapons to win in straight sets.

The second semifinal should be a closer affair. While Federer has won all five of his meetings with Cilic, their last clash was a tight three-set affair just last month. And Cilic is playing superbly, serving better than ever and displaying consistency from the back of the court as well as venom with his powerful forehand. Federer, meanwhile, was some way short of his best against Monfils, and, despite improving as the match wore on, struggled to find his rhythm all night. Were Federer to play the same way again he may not survive this time. But, helped by his net-rushing aggression, Federer have too much and win in four tough sets.

Start time: Novak Djokovic and Kei Nishikori will get underway at noon EDT on Saturday, with Roger Federer and Marin Cilic following, not before 1.30 p.m.

Tickets: Tickets are sold out, but can be purchased through Ticketmaster’s U.S. Open Ticket Exchange.

TV Channel: CBS

Live Stream info: