London - Defending champion Serena Williams survived a major scare from US compatriot Christina McHale in a thrilling Wimbledon second round encounter on Friday.
The world number one came from behind to defeat McHale 6-7 (7/9), 6-2, 6-4 in two hours and 29 minutes on Centre Court, narrowly avoiding what would have been her earliest-ever Wimbledon defeat.
Williams will face Germany's Annika Beck for a place in the last 16.
"It was a really good match. She played great and she always plays great against me," Williams said.
"I know mentally no-one can break me. I knew, down a break in the third, that I was going to have to put my mind in it and that's what I did."
Several times throughout the match, Williams was left cursing the bounce of the ball or screaming at the heavens as she struggled to find her form against the world number 65.
McHale was set point down in the 10th game of the first set but challenged when Williams thought she had won the point - and Hawk-Eye technology showed the tiniest sliver of the ball was in, giving the outsider a reprieve.
McHale recovered and fashioned a few set points for herself before sealing it on the tie break.
At the end of the first set, a raging Williams was given a warning after smashing her racquet into the ground five times after sitting down, before letting go - the racquet flying into the stomach of a television cameraman.
Williams, trying to win a Open Era record-equalling 22nd Grand Slam title, broke in the third game of the second set and went on to win it.
But the champion rode her luck in the third set. McHale hit two double faults to throw Williams a lifeline when she had the chance to go 3-1 up.
McHale was playing out of her skin, but her first serve deserted her at a critical stage and Williams broke to serve for the set at 5-4 up.
Williams then rained down three consecutive aces in the final game - she passed the 800 aces at Wimbledon mark during the match - and sealed her place in the round of 32.
As she left the court, a services steward retrieved the racquet she had thrown away, and the champion duly signed it and gave it to a fan.
Williams, 34, narrowly escaped what would have been her worst Grand Slam loss since falling to world number 111 Virginie Razzano in the first round at the 2012 French Open.