NEW YORK — While the tennis world was consumed with Serena Williams’s sprint back to the top, Roger Federer’s improbable stumble and Rafael Nadal’s marathon quarterfinal, a pair of past U.S. Open finalists quietly celebrated wins Wednesday and went on their way.

Last year’s women’s runner-up, Madison Keys, isn’t at the center of attention at the year’s final Grand Slam, though she pummeled Carla Suarez Navarro, 6-4, 6-3, in front of a loud crowd under the lights at Arthur Ashe Stadium. Kei Nishikori played a tense, four-hour rematch of his 2014 U.S. Open final against Marin Cilic and emerged victorious this time, 2-6, 6-4, 7-6 (7-5), 4-6, 6-4, but he isn’t the story of the men’s draw, either.

Keys and Nishikori are content to float through their respective draws, each of them mostly silent and dangerous.

“It’s kind of nice to be under the radar. Either way, I’m pretty used to it,” Keys said. “This one just seems like it’s a little bit more low-key.”

Left alone to focus on her tennis, the 23-year-old Keys is thriving. She dropped only a single set as she made her way back to the semifinals for the second year in a row at Billie Jean King National Tennis Center.

On Wednesday, she wielded her most powerful weapons to hit 11 forehand winners (out of 22 overall) and dropped just nine points on her first serve against Suarez Navarro. A pair of break points were all she needed to hold off the 30-year-old Spaniard who defeated a woman with a similar game to Keys’s, Maria Sharapova, on Monday.

Keys, seeded 14th, formally split with her full-time coach, David Taylor, just before this U.S. Open and has been relying on longtime adviser Lindsay Davenport, a three-time Grand Slam champion, in addition to a rotating cast of coaches from the U.S. Tennis Association. She has flaunted some of her most consistent tennis this fortnight and is the highest-seeded woman left in the draw.

She is also the only one of last year’s four American semifinalists to have booked a return trip. She made the semifinals of the French Open this year, too, making 2018 the first season of her career in which she has reached two Grand Slam semis.

“I am doing whatever I can to put myself in the position to go deeper into slams,” Keys said. “I’m feeling more comfortable in those big moments and like matches like tonight. . . . Not [putting] too much pressure on myself has really helped me do that.”

That experience in pressure-filled moments could give her an edge against Naomi Osaka in Thursday’s semifinals. It will be the No. 20 seed Osaka’s first Grand Slam semifinal. The matchup pits muscle against muscle as Keys is one of the most powerful hitters on tour and Osaka is one of the few who can step up to match that force.

Keys ousted Osaka in a tight three-set match two years ago in the third round of the U.S. Open — Osaka led 5-1 in the final set before Keys won in a tiebreaker.

“Honestly, I think she’s probably forgotten about it. I think it will be a completely different match. And she’s grown a lot since then, as have I. So I think it’s going to be a tough match, and I don’t think that’s going to be on her mind.”

The Keys-Osaka match will follow the night’s first women’s semifinal, No. 17 seed Serena Williams vs. No. 19 seed Anastasija Sevastova.

Nishikori, who skipped the U.S. Open last year with a wrist injury that shut down his season early, moves on to face Novak Djokovic. History is against the 2015 Citi Open champion, who is 2-14 lifetime against Djokovic.

The Serbian is one step closer to his 14th Grand Slam title overall and his second at the U.S. Open. The Wimbledon champion beat John Millman, 6-3, 6-4, 6-4, in just under three hours in another humid match that wasn’t always easy — he created 20 break points but converted just four and hit 53 unforced errors.

“I don’t have great record against Novak, but always, you know, it’s been a tough match last couple of years. I’ve seen chances, but I haven’t able to make the last step,” Nishikori said. “. . . Especially after coming from injury, I think I’ll enjoy the challenge.”