Serena Williams suffered the most lopsided defeat of her career as Johanna Konta battered the American great 6-1 6-0 in a shock opening-round victory the WTA Silicon Valley Classic.
Former world number one Williams was playing her first match since Wimbledon, where the 23-time grand slam champion finished runner-up, and was outclassed in just 51 minutes by 2016 victor Konta.
Seeded sixth at the WTA Premier tournament she has won three times, Williams managed just nine winners against 25 unforced errors as Konta won 12 successive games.
Prior to the defeat in San Jose, Williams' previous worst losses came against Johnnette Kruger in 1998 and Simona Halep at the 2014 WTA Finals, matches in which she managed to only win two games.
"I think she played well in the second set," Serena said after the match. "I wasn't sharp at all in the first set, and she got more confident from there. She clearly ran away with it."
"I suppose things went wrong in the second game since I won the first - it was the only game I won in the match. I'm just taking everything a day at a time. I think she played better in this match than she has in about 18 months, so that's great for her."
"I know I can play a zillion times better, but I have so many things on my mind, I don't have time to be shocked about a loss that clearly wasn't when I was at my best. I can only try to be there and fight, which is what I was doing out there. I moved a lot better, too, so I'll take the positives where I can," he said.
Next up for British number one Konta is American Sofia Kenin in the second round.
Fifth seed Mihaela Buzarnescu prevailed 6-3 4-6 6-3 against Sachia Vickery, Timea Babos (8) advanced after defeating Kristina Mladenovic 6-4 6-2 and Zhang Shuai (7) was bundled out by Vera Lapko 7-6 (7-2) 6-0.
In other matches, Heather Watson outlasted Claire Liu 6-4 3-6 6-4, while Amanda Anisimova topped Wang Qiang 6-2 7-5.