Elena Baltacha thought her second round victory against seventh seed Na Li at the BNP Paribas Open was the best of her career.
The British number one prevailed 7-6, 2-6, 7-6 in Indian Wells after an epic match that lasted almost three hours.
Baltacha, who goes on to play Australian wildcard Alicia Molik in the third round, said: "It's an unbelievable feeling. I knew that at the start of the third set I'd have to be at another level definitely, because I couldn't carry on how I did in the second set. Basically I just thought, right, this is your opportunity. This is it.
"You've got to rise above it, even if you're a bit tired. You've just got to go for it. I don't think she was playing 100 per cent and I thought, you've got a big shot here. You've really got to up it.
"At 1-5 down in the tiebreaker I just went into the zone and felt really strong and just fought my heart out. I was stunned on match point. I think it kind of took me like ten seconds to actually realise that she'd hit that backhand wide."