Britain's Andy Murray saved a match point as he came back from the brink to beat Grigor Dimitrov and reach the last eight at the Cincinnati Masters.
Second seed Murray trailed 5-2 in the final set but recovered to win 4-6 7-6 (7-3) 7-5 after almost three hours.
"There were many, many important points in that match," he said. "I'm not quite sure how I managed to get through it."
Novak Djokovic and Roger Federer also progressed, but Rafael Nadal lost 5-7 6-4 7-6 (7-3) to Feliciano Lopez.
Murray came through a huge test against Dimitrov after trailing by a set and a double break, and then losing five straight games in the decider.
"If you want to win the big competitions, you'll have to come through difficult situations," said the Scot.
"Last year, I didn't come through enough of them. I lost a lot of matches from winning positions, and this year I managed to turn that around, which was very positive."
Murray, 28, will face Frenchman Richard Gasquet next, after the 12th seed defeated US Open champion Marin Cilic 7-5 6-3.
Spain's Lopez goes on to play six-time champion Roger Federer, who beat Kevin Anderson 6-1 6-1 in only 55 minutes to reach the quarter-finals.
Top seed Djokovic hit back from a double break down in the final set to beat Belgian David Goffin and reach the last eight.
Goffin, ranked 14th, looked on course for victory at 3-0 in the decider but world number one Djokovic took six straight games to win 6-4 2-6 6-3.
Djokovic next faces a rematch of the French Open final against fifth seed Stan Wawrinka, who beat Ivo Karlovic 6-7 (2-7) 7-6 (7-5) 7-6 (7-5).
Sixth seed Tomas Berdych thrashed Tommy Robredo 6-0 6-1, and will next face Alexandr Dolgopolov, who beat Jerzy Janowicz 6-3 3-6 6-4.
In the women's event, top seed Serena Williams beat Karin Knapp 6-0 6-2, and said: "Everyone enjoys easier matches.
"I think testing is also really important, but at the end of the day if you could have only easy matches for the whole tournament I don't think anyone would object to that."
Switzerland's Belinda Benic, who beat Williams on her way to winning the Toronto title last week, earlier retired with a right forearm injury when trailing Czech seventh seed Lucie Safarova 6-2.
Sixth seed Ana Ivanovic beat Sloane Stephens 2-6, 6-4, 6-1, while there were also wins for Jelena Jankovic and Anna Karolina Schmiedlova.