Pliskova, the US Open runner-up a year ago, triumphed 3-6, 7-5, 6-4, but was forced to save a match-point in the 10th game of the second set and recover from a break down in the decider. If she can advance past Stephens, Sevastova could potentially face American Venus Williams in a semifinal.
Roared on by the Arthur Ashe Stadium crowd, Williams, who won two titles at Flushing Meadows in 2000 and 2001, overcame serve problems to set up a meeting with gritty Spaniard Carla Suarez Navarro.
The Canadian would have been the youngest Slam quarter-finalist since Michael Chang at the 1990 French Open, youngest US Open quarter-finalist since Andre Agassi in 1988 and first US Open qualifier in the last eight since Gilles Muller in 2008.
The Russian took three sets to get the job done against Halep, but a 6-3 domination in the final set made the victory seem clinical - and it was.
It was Kenin who went into the match as the higher ranked player at 139 in the world, with Sharapova seven places lower as she makes her way back up the rankings. "That's what I missed", Sharapova said.
"When you see the stress on the scheduling system because of the sheer number of matches that had to be played, it would be tough for it to be flawless for everyone", said Widmaier. Third seed and Wimbledon champion Garbiee Muguruza of Spain swept past Magdalena Rybarikova from Slovakia 6-1, 6-1 to also reach last 16.
In a men´s draw assured of producing a first-time Slam finalist, Spanish 12th seed Pablo Carreno Busta meets Argentine 29th seed Diego Schwartzman in the last-eight while South African 28th seed Kevin Anderson meets German 23rd seed Mischa Zverev or USA 17th seed Sam Querrey.
This matchup pits one of the best servers in the tournament against one of the best returners.
The Wimbledon and Australian Open runner-up, seeking her third US Open crown, will meet the victor of a later match between Wimbledon champion Garbine Muguruza, the third seed from Spain, and Czech 13th seed Petra Kvitova, a two-time Wimbledon victor.
Mitch Trubisky to play in Bears' preseason finale
Well, that will continue on Thursday, as Trubisky will start in the Bears' final preseason game against the Cleveland Browns . Cameron Meredith suffered a potentially season-ending knee injury in the Chicago Bears' 19-7 win over Tennessee on Sunday.
The only past Grand Slam champion in the lower half of the U.S. Open's men's draw is in trouble.
While Stephens only had two winners-the same number she had when dropping the second set-she didn't need to do much from the baseline, considering 19 of her 20 first serves landed in. It's like I take something away from you because you did something wrong but then I give you a hand.
Schwartzman was overwhelmed in the opening set before the 29th seed found his range to frustrate Cilic, who bowed out after wasting three chances to level for 5-5 in the fourth set. Now she's out, and Sevastova is in to the quarterfinals.
The U.S. Tennis Association says a man from Estonia has been arrested during the U.S. Open for violating a no-trespassing notice he was given previous year during the tournament for "courtsiding" - providing information about a match that can be used by gamblers. "Yeah, I'm not sure where she is". "I still think I have a lot of work to do". Haven't lost many matches in the day, so ...
"It was a tough journey that I didn't know how would end".
"It's what he does".
Sharapova said: "It's been a really great ride in the last week".
"I'd rather watch football", he said bluntly.