Emma Raducanu dug deep to battle past Colombian Camila Osorio into the quarter-finals of the Citi Open in a match played in scorching conditions in Washington.
The British number one had secured a first win of the North American hard court season through a two and a half hour battle over Louisa Chirico and was looking to build some momentum.
Defending US Open champion Raducanu, the tournament’s second seed, started brightly by going 3-0 up in the first set after an early break and hold.
After finding himself 4-2 down, Osorio, world number 67, rallied back with two breaks of his own to lead 5-4.
Raducanu, however, rallied to save two set points in the 10th game and level things as the opening set went to a tie-break.
After going 2-0 up with a mini-break, Raducanu’s serve faltered once again as Osorio led 5-3.
However, the British world number 10 showed great resilience to level before forcing a set point, which she secured with another break.
Raducanu moved 4-2 ahead in the second set and looked to be in control, but once again Osorio responded to level at 4-4 before both players lost serve.
Raducanu needed a medical time-out to treat blisters on her racket hand, which proved so costly at the Australian Open, but came back to hold as the set went into another tie-break.
The 19-year-old continued to dig deep as she dominated from baseline to edge 5-3 ahead, before sealing her first match point when Osorio sent a service return wide, winning 7-6 (5) 7-6 (4) .
“I think I died about three times in that match and I came back – honestly, I don’t know how,” Raducanu said in his post-match on-court comments.
“Camila is a great fighter. I worked so hard for every single point.
“When she comes back, the dynamic of the fight changes a little bit, so I’m just really happy to get through it.”
Both players had been medically timed out at stages during the match, Osorio for a blister on his big toe midway through the second set.
Of her own hand problems, Raducanu said: “At the beginning of the match I was fine, but then throughout the match my skin was just being ripped off – it was quite raw and open.”
Raducanu will go on to play Russian Liudmila Samsonova for a place in the last four.
The British number one said: “She’s a great ball striker and has the ability to take the game out of your hands, so for me it’s just about recovering as best I can for tomorrow.
“Both of us are going to feel it and it’s a question of who’s going to stay tough.”
In the ATP event, British men’s number two Dan Evans advanced to the quarter-finals after Taylor Fritz was unable to continue in the third set due to the damp conditions at Rock Creek Park.
American third seed Fritz had won the opening set before Evans, who defeated Britain’s Kyle Edmund in the final round, rallied to take the second on a tie-break.
As Fritz, the world number 13, continued to fight on, Evans went 4-1 ahead.
At the end of the fifth game, Fritz called for medical attention and then decided to retire, as Evans advanced 3-6 7-6 (6) 4-1. Evans will next play Yoshihito Nishioka of Japan.