US Open -- highlights of a stunning day 8

It's all over: Roger Federer waves as he walks off court after losing to Australia's John Millman in the fourth round

US Open at a glance -- day 8:

Headlines

+ Federer stunned by world number 55 John Millman

+ Sharapova crashes to birthday girl Suarez Navarro

+ Djokovic into quarter-finals for 11th time

+ Osaka first Japanese woman in last-eight in 14 years

Top results

-- John Millman (AUS) bt Roger Federer (SUI x2) 3-6, 7-5, 7-6 (9/7), 7-6 (7/3)

-- Carla Suarez Navarro (ESP x30) bt Maria Sharapova (RUS x22) 6-4, 6-3

-- Novak Djokovic (SRB x6) bt Joao Sousa (POR) 6-3, 6-4, 6-3

Sidelines

Birthday to remember

-- Carla Suarez Navarro defeated Maria Sharapova on her 30th birthday, erasing the memory of her loss last year to Venus Williams which put a dampener on her 29th birthday.

"Was a really good present for me. I was playing also last year same day against Venus Williams, and I lost. This time I don't want to feel like last year. I want to have a happy birthday, and I have it."

First impressions

-- Novak Djokovic no longer performs his party trick of imitating other players' serves and mannerisms. But that hasn't stopped others trying to mimic him.

"Andy Roddick was doing a pretty good impression of me. Right now, Nick Kyrgios maybe," said the Serb.

Well, that was weird

-- Marketa Vondrousova was not impressed by Lesia Tsurenko claiming she was on the brink of collapse due to heat exhaustion in their marathon last-16 tie.

Tsurenko was a set and 0-2 down when she said she felt so dizzy that she needed to see a doctor before going on to claim a three-set win.

"I was angry. It was weird because she called the doctor and then she was playing normally. I don't get it," said the 19-year-old who lost in three sets.

Who's saying what

"What's challenging is when you're a teenager and you have a few hundred dollars and you've got no sense of the future, you don't know where you're going to end up. You just have a dream. I think that's a lot tougher than being 31 years old and having the opportunity to do whatever I want in my life."

-- Maria Sharapova after her defeat to Carla Suarez Navarro

"@Naomi_Osaka_ sure loves herself some razzle dazzle... I'm too old for this my heart, can't take it."

-- Naomi Osaka's coach Sascha Bajin on Twitter

"I don't think I saw it, maybe the final. I didn't really want to see any matches, because I know if I see, I wanted to play."

-- Kei Nishikori missed the 2017 tournament with injury and gave the US Open a wide berth even when it came to wathcing on TV.

"Well, I'm not happy about that, but that's a rule. He can have a toilet break. I was asking (the umpire) why he's taking so long. There is no limit for a toilet break. So I think it's a rule that it's a little bit messy."

-- Joao Sousa after Novak Djokovic went off court for an extended period.