Naomi Osaka (JAPAN): US Open champion as breakout player? Unlikely, but Osaka, the 20-year-old from Japan, just the 20th seed, pulled off one of the most seismic upsets in Grand Slam history, beating her idol, Serena Williams, in a crazy, controversial match to win her first major. Osaka, who hadn't even been to a major quarterfinal before, blocked out the drama, held her nerve and played superb tennis. Osaka had already claimed one big scalp, cutting down Madison Keys, last year’s US Open finalist, in the semis. Big things have long been predicted for Osaka, and this year, with victories at Indian Wells and the US Open, she has fulfilled her enormous potential.

 

September 3, 2018 - John Millman in action against Roger Federer during the 2018 US Open. (USTA/Brad Penner)
Photo by:  (USTA/Brad Penner)

John Millman (AUSTRALIA): The 29-year-old journeyman from Brisbane, who toiled for seven years on tour before claiming his first pro-level win, scored the upset of the tournament. On the biggest court in the world, and one of the hottest and most humid nights of the fortnight, Millman knocked off five-time champ and GOAT Roger Federer, in a match that sent shockwaves around the world and precluded a Federer - Novak Djokovic quarter. Millman gave Dokovic a run for his money, too, in an entertaining match that was much closer than its straight-sets scoreline.

September 6, 2018 - Anastasija Sevastova in action against Serena Williams during the 2018 US Open. (USTA/Andrew Ong)
Photo by:  (USTA/Andrew Ong)

Anastasija Sevastova (LATVIA): The 19th -seeded, undersized Latvian – who only a few years ago quit professional tennis – had performed well in Flushing before, reaching the quarterfinals in 2016. But this year, the 28-year-old streaked to the semifinals. Sevastova, who has a tricky game and a penchant for drop shots, took out tough customers Donna Vekic and Ekaterina Makarova before toppling the seventh seed, Elina Svitolina. But she saved her best for the quarters, blitzing last year’s US Open champion, Sloane Stephens, the 3rd seed, in straight sets.

September 2, 2018 - Nikoloz Basilashvili in action against Rafael Nadal at the 2018 US Open. (USTA/Darren Carroll)
Photo by:  (USTA/Darren Carroll)

Nikoloz Basilashvili (GEORGIA): Basilashvili, from the small, former Soviet republic of Georgia and ranked just outside the 32 seeds, made his first deep foray into a Slam at the Open. One of the biggest hitters on tour, he upended the American Jack Sock, the 18th seed, and gave No. 1 Rafael Nadal fits in the fourth round with his roundhouse forehand and nuclear backhand, forcing Nadal to come up with his best tennis to move on.

September 1, 2018 - Aryna Sabalenka in action against Petra Kvitova during the 2018 US Open. (USTA/Brad Penner)
Photo by:  (USTA/Brad Penner)

Aryna Sabalenka (BELARUS): The 26th seed Sabalenka rode quite a wave this summer, reaching the semis in Cincy and winning her first WTA title in New Haven before playing in her first US Open. In the second round, the strapping Belarusian took out former US Open finalist Vera Zvonareva and in the third, two-time Slam champ Petra Kvitova. Sabalenka blew the Czech off the court before running into eventual champ Osaka’s buzz saw.

August 30, 2018 - Joao Sousa in action against Pablo Carreno Busta at the 2018 US Open. (USTA/Andrew Ong)
Photo by:  (USTA/Andrew Ong)

Joao Sousa (PORTUGAL): The 68th-ranked Portuguese, from a small town (Guimaraes) in a small country, played some big tennis in beating last year’s US Open semifinalist Pablo Carreno Busta and the 2016 quarterfinalist Lucas Pouille, the 17th seed. Sousa’s streak only ended when he met finalist/champ Novak Djokovic in the fourth round.