Britain's Jo Konta continued her remarkable run with victory over 18th seed Andrea Petkovic in the US Open third round.
Konta, ranked 97th, converted her sixth match point to win 7-6 (7-2) 6-3 and take her winning streak to 16 matches.
The 24-year-old British number two had never been past the second round at a Grand Slam before this week.
She next faces two-time Wimbledon champion and fourth seed Petra Kvitova in the last 16 on Monday.
"It's all a progression," said Konta. "I feel like I've been playing a good level of tennis all year.
"It's always a confidence boost when you get to play against the best players in the world."
It took two service games and six match points to see it out, but Konta again had too much for a player ranked well above her.
"It was definitely tough because, even if she's not feeling her best, she's one of the best competitors on the tour," said Konta.
"She definitely didn't give it to me, as you can tell from the last three games."
When Petkovic, swathed in ice towels, took a medical timeout during the second set, it was clear her challenge was fading.
Petkovic struggled in the heat and had a medical time-out
The damage had already been done, however, after Konta deservedly took a tight first set of six service breaks in the tie-break.
She had recovered from dropping serve at the start of the match and attacked the vulnerable Petkovic forehand.
Poor service games from the Briton at 4-3 and 6-5 suggested the nerves with which she has coped so well in New York were fluttering, but from 0-2 down she reeled off seven straight points in a superb tie-break.
Petkovic, now wearing a visor despite relatively kind conditions, was clearly struggling when she dropped serve early in the second, and slipped further behind after having her blood pressure taken at 0-3.
Konta came agonisingly close to victory with three match points at 5-1, but converted her second chance to serve it out after one hour and 56 minutes.
After losing to Maria Sharapova at Wimbledon, Konta racked up 10 victories while winning two challenger titles in Canada, three in US Open qualifying and now three in the main draw.
She is the first British woman to reach the fourth round at a Grand Slam since Laura Robson made the same stage at Flushing Meadows three years ago.
Another victory would make her Britain's first female Slam quarter-finalist since Jo Durie at Wimbledon in 1984.
Winning sixteen matches in a row is something most professional tennis players will never experience, bearing in mind it takes five or six to win most tournaments.
Konta recorded 10 wins while claiming two titles on the lower challenger tour after Wimbledon, although Vancouver is at the upper end of that scale and not far off WTA quality. She then won three matches in qualifying, and now three in the main draw.
Konta has now guaranteed herself at least £141,000 for reaching the fourth round - more than four times her previous biggest pay cheque.
She is also set to take a significant climb in the world rankings from her current position of 97, with a current projection of around 58th should she end her run in round four.
That is likely to leave her tantalisingly close to the British number one spot, with Heather Watson expected to be around 56th when the new rankings are released after the US Open.