Slightly over a month after winning Wimbledon, Novak Djokovic is in another semifinal. Djokovic swept John Millman, 6-3, 6-4 6-4, to advance to the US Open semifinals on Wednesday, continuing what's been a remarkable return to form. Millman broke Djokovic's serve just once, whereas Djokovic broke Millman's serve four times.

It was a very strange match, with Djokovic almost losing his cool after receiving two warnings for time violations, ultimately losing a game for it. Both players stopped play numerous times to change outfits, with the heat making it incredibly uncomfortable on both Millman and Djokovic.

It was an impressive effort on Millman's part, but it's nothing Djokovic isn't used to. This will be the 11th time in 12 years he's appeared in a US Open semifinal. He'll be facing Kei Nishikori, who upset Marin Cilic to advance to his third career Grand Slam semifinal -- all three coming in the US Open.

The No. 21 ranked Nishikori defeated No. 7 ranked Cilic in five sets, 2-6, 6-4, 7-6, 4-6, 6-4. It wasn't the cleanest of matches as the grueling heat at Arthur Ashe Stadium seemed to force both competitors into a slew of mistakes over the course of the four-plus hour match. Ultimately, though, Nishikori prevailed and stamped his ticket to the final four. 

Meanwhile, the women's draw at the 2018 US Open belongs to the lower seeds. Naomi Osaka took her place in the semifinal with a win over Lesia Tsurenko in straight sets on Wednesday. 

Osaka, who is just 20 years old, is having a terrific 2018 season. She won the Indian Wells Open and made it to the fourth round of the Australian Open. This is her first career Grand Slam semifinal in what's been a year of firsts for her so far. She's also the first Japanese woman to make the US Open semifinals in 22 years.

Against Tsurenko, Osaka barely broke a sweat, winning, 6-1, 6-1. She won 20 of her 22 first serves, and she broke Tsurenko's serve five times. Tsurenko had 31 unforced errors to Osaka's 11, and Osaka finished with 12 winners.

It was just the latest in what's been a dominant run for Osaka. So far in this Open, she's held opponents scoreless in three sets, and she's dropped only one set thus far. Now, she needs to do it one more time to advance to her first career final. 

Osaka's next opponent will likely be her toughest yet, as she's set to face Madison Keys in the semifinals. 

Keys punched her ticket with a victory over Carla Suarez Navarro on Wednesday. The 23-year-old Keys beat Suarez Navarro in straight sets, 6-4, 6-3. This will be Keys' second consecutive semifinal appearance at the US Open.

After Suarez Navarro pulled off a stunning upset win over Maria Sharapova earlier in the week, she was eventually overpowered and outmatched by Keys in Wednesday's quarterfinal. The match started off as a back-and-forth affair, but Keys was able to pull ahead to claim the first set and never really looked back.