King, a 24-year-old former University of Michigan All-American ranked No. 392, stunned No. 2 seed Yoshihito Nishioka of Japan 6-4, 7-5 in a first-round matchup of left-handers at the Seascape Sports Club.
Nishioka, only 5-foot-7 (1.70 meters), reached his first ATP World Tour semifinal last week in Atlanta and advanced to the Aptos quarterfinals last year. He's ranked a career-high No. 85 overall and second in Japan behind No. 7 Kei Nishikori.
Also falling today were No. 4 Stefan Kozlov of Pembroke Pines, Fla., No. 5 Ramkumar Ramanathan of India and No. 7 Farrukh Dustov of Uzbekistan.
In the featured evening match, No. 3 Bjorn Fratangelo avoided the rash of upsets. The 23-year-old American topped 29-year-old countryman Alex Kuznetsov 6-2, 7-6 (4). Fratangelo reached last year’s semifinals, and Kuznetsov won the title 10 years ago.
After the first round, the only remaining seed in the bottom half of the draw is No. 6 Ernesto Escobedo of the United States. He leads the U.S. Open Wild Card Challenge after two of three tournaments ($50,000 Binghamton, N.Y., $50,000 Lexington, Ky., and Aptos). The American who earns the most points in two of the tournaments will receive a wild card into the U.S. Open, Aug. 29-Sept. 11 in Flushing Meadows, N.Y.
Kozlov, 18, lost to 21-year-old wild card Mackenzie McDonald of Piedmont, Calif., 6-1, 6-4. Piedmont is located in the San Francisco Bay Area about a 90-minute drive north of Aptos.
Kozlov, one of the United States’ top prospects, advanced to his first ATP quarterfinal at s-Hertogenbosch, Netherlands, in June.
McDonald turned pro in May, forgoing his senior year at UCLA, after becoming the first man in 15 years to sweep the NCAA singles and doubles titles.
Ramanathan lost to qualifier Cameron Norrie of Great Britain 6-3, 7-6 (8). Norrie attained the NCAA singles semifinals as a sophomore at Texas Christian University in the spring.
Dustov, an Aptos semifinalist as a qualifier three years ago, bowed out to Australian veteran Marinko Matosevic, a former top-40 player and the 2010 Aptos champion, 6-1, 6-0.
Wild card Clay Thompson, a former UCLA All-American, beat qualifier John Lamble of Saratoga in the Bay Area 6-3, 6-4.