ICYMI: Madison Keys clinical in victory against Carla Suarez Navarro

Robert Deutsch/USA TODAY Sports

NEW YORK -- For a second straight year, a new American could be crowned the US Open women's champion.

Last year it was Sloane Stephens. This year it could be Madison Keys.

Keys, runner-up a year ago, proved too good for the No. 30 Carla Suarez Navarro at Arthur Ashe Stadium yet again. Keys has won all four matches the two have played, though this is the first time Keys walked away the winner in straight sets.

This is Keys' second consecutive US Open semifinal and her second Grand Slam semi of the year (She also made it to the semis at the French, where she lost to Stephens). Keys has been to at least the quarterfinals in four of the past five majors.

"I feel like a lot of my matches last year were emotional roller coasters," Keys said. "This year I have been much more solid mentally. In tougher times I've been keeping my cool a little bit better and not having the big emotional swing to try to get back into matches."

Olympic champion spotted: The entire U.S. tennis team had gone to watch Katie Ledecky compete at the Rio Olympics. Now, Ledecky is doing her part, as she cheered Keys from the sidelines.

History at US Open: Japan had a big day Wednesday at the US Open. First, Naomi Osaka bulldozed her way into her first major semifinal after dropping Lesia Tsurenko -- 6-1 6-1. It wasn't as easy for Kei Nishikori, who had to battle out a five-set marathon against No. 7 Marin Cilic to make his third US Open semifinal.

It was the first time in the Open Era that a Japanese man and woman are in the semifinals of a grand slam.

When asked during her media conference about Nishikori, Osaka said, "I don't know if I'm going to get in trouble if I say this. I think [Kei] is a really big kid. He plays [video] games and stuff, too. I think we're pretty similar in that sense."

Nishikori had his to say.

"She looks mature," he said. "She looks older, but when we talk, she's also a kid. We don't play the same [video] games. I wish we can play the same game. Maybe in the future, We gotta talk [about that]."

A friendship definitely seems to be budding.

Sportsmanship on display: Fans were still buzzing from the near five-hour marathon Tuesday between defending champion Rafael Nadal and No. 6 seed Dominic Thiem. Apparently, so is Thiem. Though the Austrian did not end up on the winning side, he had only good things to say about Nadal and the match.

Mixed doubles action: Coming back from a brutal knee injury (remember when she fell on the court during a net point at Wimbledon in 2017 and had to be rushed to the hospital?), Bethanie Mattek-Sands is through to the final of the mixed-doubles event with Britain's Jamie Murray. The pair defeated the American pairing of Christina McHale and Christian Harrison that ended in a thrilling match tie-break, 6-4 2-6 10-8.

Judy Murray, Jamie's mother, also seems to be enjoying her son's performance.

The legend is back: Two-time US Open champion Andre Agassi was courtside for Nishikori's five-set win over Cilic.