Billie Jean King, whose comeback was the talk of Wimbledon this year, checked out of singles play at the US Open after just one match. The four-time champion was upset in the first round by 18-year-old Susan Mascarin of Grosse Pointe Shores, Mich., 6-3, 6-2.
Asked if overconfidence had been a problem, the 38-year-old King replied, ''For her or me?'' Billie Jean knows how well youth has been served at the Open, where Chris Evert, Tracy Austin, and Andrea Jaeger burst into prominence.
Absent from the circuit most of the last two months, Billie Jean lacked precision and match toughness, yet indicated she's not giving up and expects to be back next year.
On the men's side, fifth-seeded Vitas Gerulaitis was beaten in straight sets by Fritz Buehning, a New Jersey resident known as much for his temper as his tennis, while seventh-seeded Argentine clay court specialist Jose-Luis Clerc also was upset in the first round, losing a fifth set tiebreaker to Kim Warwick. Gerulaitis, a New Yorker who has reached the finals and semifinals in previous appearances here, called the effort his worst ever in a major tournament but would not comment on whether it had been affected by his entanglement in a federal drug trial in New York. Gerulaitis's name was mentioned by government witnesses who quoted the defendant as having said that Vitas had been willing to participate in the purchase of cocaine, but the player's lawyer said his client was not involved.