Former world No 1 lost her first ever night match in New York, while Tsurenko overcame heat exhaustion to reach the last eight
Sharapova knocked out of US Open as Keys and Osaka advance to quarter-finals
Maria Sharapova was knocked out of the US Open in the fourth round on Monday, losing 6-4, 6-3 to Spanish birthday girl Carla Suarez Navarro who inflicted the Russian's first ever night-time loss at the tournament.
Sharapova, the 2006 champion who was trying to reach the quarter-finals for the first time since 2012, hit 38 unforced errors and dropped serve six times.
The defeat ended the former world No 1's perfect record of 23 wins - 22 of them on Arthur Ashe Stadium - in night sessions at Flushing Meadows.
Suarez Navarro, who celebrated her 30th birthday Monday, was a quarter-finalist in New York in 2013.
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"Maria has played here at night many times so I knew I needed to be aggressive, focussed and play solid," said the 30th seeded Spaniard after clinching a second win in six meetings with Sharapova.
"I told myself to run and fight - that's the way I can play really good tennis."
Suarez Navarro will face 2017 runner-up Madison Keys for a place in the semi-finals.
"Madison is from the United States so I guess all the crowd will be for her," she said. "I have played her a few times. She has a great serve and plenty of experience on this court."
Sharapova, who won the last of her five grand slams at Roland Garros in 2014, has endured a disappointing return to the majors since the end of her doping ban in April 2017.
She made the fourth round in New York last year, third round in Australia in January, quarter-finals in Paris before a first round exit at Wimbledon.
The Russian's loss to compatriot Vitalia Diatchenko, the world No 132 at the time, at the All England Club was her first opening round Wimbledon defeat and earliest grand slam exit in eight years.
"I definitely expected more from the slams this year," Sharapova, 31, said. "But I have the motivation and belief every day to continue."
Keys made the last-eight with a 6-1, 6-3 win over Slovakia's Dominika Cibulkova. The other quarter-final in the bottom part of the draw will see Japan's Naomi Osaka face Lesia Tsurenko of Ukraine.
Osaka, the 20th seed, made the last-eight of a major for the first time by beating Aryna Sabalenka of Belarus 6-3, 2-6, 6-4.
Tsurenko also made sure of a first quarter-final at the slams by seeing off Czech teenager Marketa Vondrousova.
Osaka reached her first grand slam quarter-final, tearfully admitting she was prepared to "break a leg" to win the match.
Osaka, 20, became the first Japanese woman in the US Open last-eight since Shinobu Asagoe in 2004.
Osaka, seeded 20, came back from a break down in the final set to take the tie on a fourth match point when Sabalenka served up an eighth double fault.
"I would never have forgiven myself if I had lost that match," said Osaka. "When I was a break down in the final set I thought I would even break a leg if needed so I could get to every ball."
Tsurenko, 29, had been on the brink of collapse due to heat exhaustion before seeing off Vondrousova.
World No 36 Tsurenko was a set and 0-2 down when she bent double on the sizzling Grandstand court, looking increasingly unsteady in the 33-degree heat and crushing humidity.
"I was really dizzy and I asked nature or God or somebody please move the shade over faster," said the woman who put out world No 2 Caroline Wozniacki in the second round.
In the two-hour 32-minute match, which featured 13 breaks of serve, Tsurenko committed 57 unforced errors while 19-year-old Vondrousova hit a huge 73.
The Czech world No 103 thought that Tsurenko was exaggerating her distress.
"I was angry. It was weird because she called the doctor and then she was playing normally. I don't get it," she said.
The two other quarter-finals will feature six-time champion Serena Williams against Karolina Pliskova, the Czech eighth seed, while third seed and defending champion Sloane Stephens faces Latvia's Anastasija Sevastova.