"She never let me in," said King, who is 25. "She's played at such a high level for so long, and I used to watch when I was a kid, growing up. So it's kind of surreal to see the person that you've been watching on TV in front of you and playing. It was difficult."
While buzz around the tournament grounds built all day waiting for 15-year-old CiCi Bellis to play her second-round match at night she wound up losing Williams ran her U.S. Open winning streak to 16 matches as she tries to become the first woman to win three consecutive titles at Flushing Meadows since Chris Evert took four in a row from 1975-78.
For the moment, the 32-year-old Williams wants to stay focused on avoiding the sort of problems she had at the Australian Open (where she lost in the fourth round), French Open (second round) and Wimbledon (third round). Not since 2006 has she failed to reach at least one major final in a year and she only entered two Slams that season.
So far this week, she's left the trouble to others, and Williams could wind up being the beneficiary. A pair of other past major champions, No. 8 Ana Ivanovic and No. 24 Sam Stosur, lost Thursday, as did No. 23 Anastasia Pavlyuchenkova and No. 27 Madison Keys, bringing the total to 11 seeded women gone after only two rounds.
That included No. 12 Dominika Cibulkova, the Australian Open runner-up who was surprisingly defeated Tuesday by Bellis, the youngest player to win a match at the U.S. Open since Anna Kournikova in 1996. Bellis, a Californian ranked 1,208th and playing in her first tour-level event, lost Thursday in three sets to 48th-ranked Zarina Diyas of Kazakhstan.
In other action under the lights, 2012 U.S. Open champion Andy Murray won in straight sets, before Wimbledon finalist Eugenie Bouchard faced Sorana Cirstea in the day's last match.
Williams could have faced Stosur the woman who beat her in the 2011 U.S. Open final in the fourth round, and 2008 French Open winner Ivanovic in the quarterfinals.
"You always hear about who is winning, who is losing. You hear about upsets. But for me, especially lately, I have to worry about my first round, my second round, and my third round. I can't get too far ahead of myself," Williams said.
"I was a casualty before, so ... I can't make anything of it," she said of the rash of seeded losers. "At this point, I'm trying to stay alive."
After her singles victory, Williams went out and paired with older sister Venus for a first-round win in doubles. She last time Serena was seen competing in doubles at a major, last month at Wimbledon, she looked disoriented in warmups, then served four consecutive double-faults and quit after three games, saying she was ill.
Ivanovic had seven double-faults among her whopping 29 unforced errors in a 7-5, 6-4 loss to 42nd-ranked Karolina Pliskova of the Czech Republic, who occasionally plays doubles with her twin sister and never had been to the third round at a major.
Ivanovic, a former No. 1, wraps up 2014 with only one major quarterfinal to her credit, at the Australian Open.
"I had great lead-ups to every Grand Slam. I played a lot of matches and won lot of matches," she said. "At the Grand Slams I just haven't performed that well."
Stosur, meanwhile, was edged 3-6, 6-3, 7-6 (8) by 50th-ranked Kaia Kanepi of Estonia.
There have been fewer surprises among the men so far, and only one seeded player was sent packing Thursday afternoon, when No. 28 Guillermo Garcia-Lopez of Spain was defeated by Sam Querrey of the United States 6-3, 6-4, 6-4.
Querrey now faces an even tougher task: He takes on No. 1-ranked and No. 1-seeded Novak Djokovic.
Among the noteworthy results Thursday was the 7-6 (2), 4-6, 6-4, 6-2 win by Victor Estrella Burgos of the Dominican Republic against Borna Coric of Croatia. Playing in the U.S. Open for the first time at age 34, Estrella Burgos eliminated a player half his age in the 17-year-old Coric.
O Cici Bellis, the 15-year-old from California the youngest player to win a match since Anna Kournikova in 1996 during the first round loses in the second round Thursday.
• Ana Ivanovic has seven double-faults in her loss to Karolina Pliskova.
• American Sam Querrey advances to face No. 1-ranked Novak Djokovic.