World number one Dinara Safina scrambled past Italian Roberta Vinci 2-6, 7-5, 6-4 to reach the third round of the Cincinnati Open on Tuesday.
World number 46 Vinci served for the match at 5-4 in the second set but her nerve failed her at the crucial time.
"It was a day when nothing was going [right]," Safina told reporters. "Everything was going all over the place.
"So I just accepted it. I thought that if I lose I just have to forget this match as soon as possible, because it makes no sense. It's not me, not my normal game."
With Safina spraying the ball everywhere, Vinci took advantage to lead by a set and 3-0.
Top seed Safina called for her coach and after a quick consultation, things began to change for her and she got back on level terms at 3-3.
Nevertheless, Vinci broke again to lead 5-4 but could not serve out and the Russian snatched the set before recovering from a break down in the decider to clinch victory.
"At 3-0 I called my coach and he said maybe change the racquet," Safina said, adding that the humid conditions made the balls fly more than normal. "Maybe also this helped me.
"Slowly I think she got tight. I don't know what happened to her because I was completely off. I guess she was not ready to beat me. She got afraid and things turned around."
French Open champion Svetlana Kuznetsova also survived a scare and two rain breaks to beat Czech Lucie Safarova 6-3, 6-7, 7-6 after two hours, 18 minutes.
Third seed Venus Williams had no such problems, drilling eight aces as she crushed Olga Govortsova of Belarus 6-2, 6-2 to reach round three.
Italian 14th seed Flavia Pennetta picked up where she left off after her title win in Los Angeles last week with a crushing 6-2, 6-3 first round victory over Japan's Ayumi Morita.
In other first-round action, Daniela Hantuchova recovered from a slow start to beat Italy's Sara Errani 3-6, 6-3, 6-1 in a match lasting more than two and a half hours.
Poland's Agnieszka Radwanksa, the 13th seed, overpowered Japan's Ai Sugiyama 6-2, 6-1 while Belgian qualifier Yanina Wickmayer upset Italian Francesca Schiavone 6-3, 6-4.