A “light-headed” Johanna Konta was given the option of retiring during her Fed Cup win over Serbia’s Aleksandra Krunic by captain Anne Keothavong.
The exhausted British number one – playing her third three-set match is as many days – was slumped on the floor during a break after the second set.
But she recovered to win 7-6 (7-1) 3-6 6-2, sending GB into April’s play-offs.
“She didn’t have to continue if she felt like she couldn’t, but she wanted to,” Keothavong said.
“She showed so much courage and determination to find a way.”
Konta’s defiant win and an earlier 6-4 6-3 victory for an in-form Katie Boulter over Ivana Jorovic clinched Saturday’s tie for Britain in Bath, sending them through to their third consecutive World Group II play-off.
Great Britain – bidding to return to the World Group for the first time since 1993 – were playing on home soil this week for the first time in 26 years and won all of their rubbers across four fixtures in four days, with Boulter and Konta winning all of their singles rubbers.
I felt ‘out of body’ – Konta
Konta, who needed to be helped to her feet at the end of her win over Krunic, was seen lying on the floor in a gangway during a comfort break between the second and third sets.
“I progressively just started feeling more and more unwell, feeling light-headed, shaky, feeling a little bit out of body,” the 27-year-old world number 39 said.
“It got the better of me at the end of the second set. I really just tried to not panic, and just assess what I could do and basically do the best that I could with that.
“I had to quickly assess what my limitations were. I tried to zone in on the ball and time it as well as I could and try to direct the ball as well as possible, and I was able to do that, which made it difficult for her to do what she wanted with the ball, which I think is what basically enabled me to come through.”
Keothavong told BBC Radio 5 live: “Going into this match, I knew fatigue could possibly be an issue. It’s been a tough week.
“Every match she has played this week has been incredibly tough.”
Asked if Konta came close to retiring after the second set, Keothavong replied: “I gave her the option.
“She said she wanted to keep going, to give herself a chance, to give herself the opportunity to win her match for the team.
“She should be really proud of herself, because we all are.”
Boulter said she was “so proud” of Konta, adding: “She worked so hard and pushed through barriers I’m sure she didn’t want to go through today.”
‘A long timeout’
Krunic said she had thought Konta had taken “a very long timeout” but that if she had health problems then she could not complain.
“It’s difficult for everybody. None of us are fresh,” the Serb said.
“If she almost fainted and she was lying on the ground, then take as long as you need to get up.
“Regarding her play, I didn’t see anything wrong with her on the court.”
What happens next?
Great Britain now await Tuesday’s draw [12:00 GMT] for the play-offs that will offer the chance of promotion to the second tier of women’s team tennis and Keothavong has one simple wish.
“A home tie,” she said.
There will be eight teams in the play-offs, including the other three winners of this week’s regional third-tier events and the four sides who lose World Group II ties this weekend.
It is at this stage that Great Britain have fallen four times in the past seven years, most recently last April when they lost the deciding doubles rubber against a Japan team that featured current world number one Naomi Osaka.