Roger Federer crashes out of US Open

John Millman surprised everybody, including himself by battling past Roger Federer 3-6, 7-5, 7-6 (9/7), 7-6 (7/3) at Flushing Meadows on Monday evening, to send the world No. 2 crashing out of the US Open in the round of 16.

The 55th-ranked Australian had never before beaten a top-10 player and never before had Federer lost to a player ranked below the top-50.It was also Federer's earliest US Open exit since he fell in straight sets to Tommy Robredo in the fourth round in 2013.

"I'm probably in a little bit of disbelief," Millman, 29, said in the on-court interview after three hours and 35 minutes in the cauldron of Arthur Ashe Stadium.

"I have so much respect for Roger and everything he's done for the game. He's been a hero of mine."

The 37-year-old Swiss committed a shocking 77 unforced errors and 10 double faults, including two in the final tie-break. After the match, he admitted that the heat had gotten to him on the night.

"I just thought it was very hot tonight," Federer said. "It was just one of those nights where I guess I felt I couldn't get air…for some reason I just struggled in the conditions tonight."

"Today he was definitely not at his best," Millman conceded. "But I'll take it."

Last German eliminated

Earlier, the last remaining German player in the tournament was eliminated as Japan's Kei Nishikori, who reached the final at Flushing Meadows in 2014, made short work of Philipp Kohlschreiber 6-3, 6-2, 7-5.

With temperatures in New York causing problems for the players, the match time of just over two hours could prove beneficial to Nishikori in the latter stages. He will now face Marin Cilic of Croatia in the last eight.

Though he got past highly-regarded compatriot Alexander Zverev in the last round, each of the 34-year-old Kohlschreiber's victories at this year's tournament have been over four sets and the physical exertion seemed to take its toll on him. 

Nishikori received an early gift when Kohlschreiber double faulted and then made an unforced error in his first service game to hand his opponent the earlist possible break. Nishikori never looked back, wrapping up the opener in a shade over half an ho second set followed a similar pattern with the German, who looked increasingly agitated by the heat, giving up his serve again in the opener and making a string of errors under little pressure.

Nishikori was a little less ruthless come set three, missing a simple volley to break his opponent early on. Although Kohlschreiber showed a few more signs of resistance, Nishikori took his next chance to break and, after missing his first chance to seal the match on serve, broke his opponent again before sealing the win.

Kohlschreiber's exit comes just two days after Angelique Kerber became the last German in the women's draw to be knocked out. The 2016 champion's campaign was ended by Dominika Cibulkova on Saturday.

Elsewhere, Novak Djokovic eased past Joao Sousa of Portugal 6-3, 6-4, 6-3 – the No. 6-ranked Serbian will be Millman's opponent in the quarterfinals.