NEW YORK -- Roger Federer and Stan Wawrinka don't share the sibling bond that Venus and Serena Williams do.
But they are friends, countryman and Davis Cup teammates who led Switzerland to the title in 2014.
Now the two men will meet in a US Open semifinal on Friday, with the winner advancing to Sunday's championship match, and the loser presumably going home.
"For Switzerland it's huge that we have two guys in the semis of the US Open, a huge tournament, biggest arena in the world," Federer said. "It's what it's all about. I think we are both very much pumped up that that's the case. Only better scenario would have been in the finals, but this is already very, very good."
Switzerland, by the way, has a population of 8 million and has two US Open men's semifinalists, while the United States, a nation of 318 million, has none.
Novak Djokovic of Serbia will meet defending champion Marin Cilic of Croatia in the first semifinal beginning at 3 p.m. Friday, with Federer-Wawrinka to follow.
At 34, Federer is five years older than Wawrinka, who is just now coming into his own at the top of the game. Since 2014, Wawrinka has twice as many Grand Slam singles titles (2) as Federer (0) and Rafael Nadal (1) combined.
"It took him a while to figure out exactly what his possibilities were," Federer, winner of a record 17 major titles, said of Wawrinka, who won the 2014 Australian Open and 2015 French Open. "I don't think he was a guy who always had enough confidence. I always thought he was a better player than he actually was, but somehow something was holding him back maybe.
"I'm happy he found that level of play. Two slams, got Davis Cup, Olympic gold. Has a complete career. Won a Masters 1000. Has everything he ever wanted. He has had a wonderful career."
Federer is 16-3 against Wawrinka, with all three of Wawrinka's wins coming on clay, including in the quarterfinals of the French.
Wawrinka knows it won't be easy to stop the Federer Express at this event, where he hasn't dropped a set and is motivated to reach his first final since 2009.
"He's feeling really good at the moment," Wawrinka said of Federer. "I think probably what he did between Wimbledon and Cincinnati with his fitness trainer was something really good for him. You can feel he's fresh and he always enjoy [tennis]. We love to watch him since more than ten years. More than that. He always do shot that no one can do. That's why he's the greatest."
Even with so much on the line, the two men said they will enjoy a laugh in the locker room before the big match.
"So [Friday] it's always the same," Wawrinka said. "We are good friend. Really close friend. We always laugh together. Friday we're gonna laugh together in the locker because we have locker next to each other before the match.
"We are going to go into the match trying to win. Doesn't matter how, but try to win. Then after the match it's back to normal."
Follow Adam Zagoria on Twitter @AdamZagoria for updates throughout the U.S. Open.