372178 11: FILE PHOTO: Sisters Serena, left, and Venus Williams shake hands after a game 1991 in Compton, CA. Serena and Venus Williams will be playing against each other for the first time July 6, 2000 in the tennis semifinals at Wimbledon. (Photo by Paul Harris/Online USA)
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372178 11: FILE PHOTO: Sisters Serena, left, and Venus Williams shake hands after a game 1991 in Compton, CA. Serena and Venus Williams will be playing against each other for the first time July 6, 2000 in the tennis semifinals at Wimbledon. (Photo by Paul Harris/Online USA)
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Serena Williams argues with the chair umpire during a match against Naomi Osaka, of Japan, during the women's finals of the U.S. Open tennis tournament at the USTA Billie Jean King National Tennis Center, Saturday, Sept. 8, 2018, in New York. (Photo by Greg Allen/Invision/AP)
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Serena Williams is usually the one who inflicts heavy defeats on others, but the former world No.1 suffered the most one-sided loss of her illustrious career Tuesday when she was knocked out of the first round of the Silicon Valley Classic after a 6-1 6-0 defeat.

During a 53-minute rout, British No.1 Johanna Konta, ranked 48th in the world, won 12 games in a row – including two service games to love in the second set – to progress to the second round in San Jose.

Williams, a 23-time grand slam champion who only returned to the tour from maternity leave earlier this year, served seven double faults and made 25 unforced errors in, according to the WTA, the most one-sided loss of her career.

READ: What my life-threatening experience taught me – Williams

Since turning professional in 1995, the 36-year-old Williams had never before lost a match without winning at least two games.

“I think she played well in the second set and I think I wasn’t sharp at all in the first set and she got confident and she clearly ran away with it,” Williams, who reached the Wimbledon final earlier this month, told reporters.

Konta, who was a career-high No.4 in the world last year, becomes the first Briton to beat Williams.

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“She obviously wasn’t playing anywhere near her best level but I was just trying to play the match on my terms and do what I can out here and put aside the incredible champion she is and play the player on the day,” Konta said in an on-court interview.