Even Roger Federer is wowed by how well he's playing at 34 and the ease with which he's winning at this US Open.
Federer is into his 10th semifinal at Flushing Meadows, and record 38th at all major tournaments. To get back to his first final in New York since 2009, he'll have to beat someone he knows quite well: Swiss Olympic and Davis Cup teammate Stan Wawrinka.
The No. 2-seeded Federer and No. 5 Wawrinka won quarterfinals about as handily as can be Wednesday night.
Federer never faced a break point, compiled a remarkable 50-8 advantage in winners, and needed less than 1 1/2 hours to dismiss 12th-seeded Richard Gasquet of France 6-3, 6-3, 6-1.
"It's nice to play this way," Federer said. "And, maybe at my age, to run through five opponents the way I have done here at the US Open, I don't consider that normal, to be quite honest, even though I expect it in some ways."
Not only has Federer won all 15 sets he's played, he has only dropped 44 games. He has won 67 of his 69 service games. And he's done it while playing attacking tennis; against Gasquet, he won the point on 22 of 28 trips to the net.
"I don't feel like I'm as old as I am. I still feel young," Federer said. "So it's nice to get rewarded with the hard work and (know) that, actually, I'm able to play sort of 'fun' tennis."
He hasn't won a major title since Wimbledon in 2012, losing finals there to No. 1 Novak Djokovic last year and this July.
"It's just nice to see how he's moving," Wawrinka said about Federer. "You think he's flying on the court."
And make no mistake: Wawrinka has been watching. He even pulled out one of Federer's tricks — a recently developed tactic of charging to the service line for a second-serve return — while eliminating 15th-seeded Kevin Anderson of South Africa 6-4, 6-4, 6-0.
The match took 1 hour, 47 minutes in all, but the third set, in particular, was dominated by Wawrinka, who won 24 of its 29 points.
Wawrinka solved the 6-foot-8 Anderson's serve, converting 5 of 8 break points. Anderson had been broken a total of four times through his first four matches combined, including his surprise of 2012 US Open champion Andy Murray.
Most of his career, Wawrinka has lived in the shadow of his older — and far more successful — countryman, Federer. Wawrinka didn't break through with his first Grand Slam title until the 2014 Australian Open. He added No. 2 this year at the French Open, beating Federer in the quarterfinals along the way.
Still, that was only Wawrinka's third victory in 19 career matches against Federer. They're good friends and paired up to win a gold medal in doubles at the 2008 Olynpics.
"Stan played a wonderful match against me in Paris, and I was very happy for him that he went on to win the tournament. He deserved it. He's been such a great player throughout his career. He improved a lot, kept on working really hard," Federer said.
"Couldn't be happier to play him here, to be quite honest," Federer added. "Two Swiss in the semis of the US Open — it's very cool for both of us."
In Friday's other semifinal, Djokovic will face defending champion Marin Cilic. Djokovic won all 13 previous meetings.
Halep wins
Romanian second seed Simona Halep and Italy's Flavia Pennetta advanced to a US Open semi-final matchup by ousting two-time Grand Slam champions Victoria Azarenka and Petra Kvitova.
And now the only obstacles to Serena Williams completing a calendar Grand Slam are players all seeking a first major title.
Halep reached her first US Open semi-final on Wednesday by defeating two-time Australian Open champion Azarenka 6-3, 4-6, 6-4.
"I don't know where I found the power to win this match," Halep said. "I'm really happy because I really wanted to go to my first semi-final here."
Italy's 26th-ranked Pennetta upset Czech fifth seed Kvitova, a two-time Wimbledon winner, by 4-6, 6-4, 6-2 in the first quarter-final at Arthur Ashe Stadium.
Pennetta has a 3-1 career edge in matches against Halep.
"I know I have to fight for every ball, to play every ball like the last one," Halep said of playing Pennetta. "I know she is a tough player but I can be strong one more day."
Williams, seeking her seventh US Open crown, has a head-to-head edge on her possible finals foes — 7-0 over Pennetta and 6-1 over Halep.
Azarenka, who lost to Williams in the 2012 and 2013 US Open finals, made 42 unforced errors to only 19 by Halep and the 20th seed from Belarus had 38 winners, two fewer than Halep.
Azarenka, 26, beat Halep, 23, twice in 2012 in their only prior matchups but Halep has won three titles so far this year while Azarenka has been nagged by a thigh injury.
Halep, the first Romanian in the US Open last four since Irina Spirlea in 1997, returned from a third-set rain break and blasted an ace to level at 2-2.
Azarenka sent a backhand wide to hand Halep a break and a 4-3 lead and they held serve to the end, which came when Azarenka sent a forehand long after two hours and 40 minutes.
Pennetta matched her best Grand Slam run from the 2013 US Open semi-finals, where she eventually lost to Azarenka.
"I'm really happy right now," Pennetta said. "I was just trying to fight every ball, running and push everything I can. I didn't think to get through this match. In the second set I was playing and playing — it was unbelievable."
Kvitova's ouster removed a potential threat to Williams who delivered one of only two Williams losses this year when they met in May on Madrid clay.
Kvitova, the first Czech woman in the US Open's last eight since Daja Bedanova in 2001, made 60 unforced errors to only 16 for Pennetta.
The fifth seed also had nine double faults against only four aces.
"It's the tension for the match, for what you think, what you have to be, what you want to be, have to do — it's everything in your mind. You have to take it out and just play" Pennetta said.