Dominika Cibulkova was ecstatic with the way she thrived on the pressure to beat Simona Halep before Angelique Kerber sealed an unlikely place in the last four of the WTA Finals for the Slovakian.
Seventh seed Cibulkova needed a straight-sets victory over Halep to have any chance of advancing to the semi-finals and won 6-3 7-6 (7-5) in the first match of the day in Singapore.
The world number eight still had to rely on Kerber getting the better of Madison Keys in the final Red Group contest and the top seed delivered, winning 6-3 6-3 to maintain her 100 per cent record in the tournament.
Finals debutant Cibulkova had lost her first two matches this week and the 27-year-old was thrilled that she was able to raise her game to prolong her season.
She said: "This win is really, really big for me. I feel relieved. I'm really, really happy about my win, about the way I played and the way I handled the situation and the pressure.
"It seems like I'm playing my best tennis under biggest pressure. You know, it's just a great feeling, to beat Simona in two sets - knowing that if I want to go further in the tournament, I have to beat her in two sets. That made me even stronger in the second set."
Halep, playing with a heavily strapped left knee, would have made the last four if she had taken a set off Cibulkova and the third seed hung in there under severe pressure from the fired up underdog.
Cibulkova added: "I wasn't even thinking about her. A few times in the second set I had - there was few times I was like, 'Okay, this can't be happening'. I was playing such good rallies, and then somehow she put the ball back again. So there were few situations I was like, 'Okay, I want to leave the court. This is unreal'.
"That's what made me so strong also, the mental toughness, that I knew I cannot lose even one point. I have to just think about what I want to do on the next point.
"That's what made me win the second set. It was extremely tough mentally and physically, but tennis-wise because it was such a high level."
Halep felt she could have altered her tactics, but was full of praise for Cibulkova.
"I think she played well. With her forehand she was dominating the match and I was very far back. I should have mixed up my shots a little bit more, to play more wide, and to make her run." said Halep.
"I tried, but it wasn't enough. But mentally I was fighting until the end, so I'm okay with the match, with the way that the match went. But not happy because I lost it."