Stanford grad Bradley Klahn, in just his second tournament since July 14, dropped a 6-4, 4-6, 6-3, 7-5 decision to Russian Andrey Kuznetsov in the first round of the US Open in New York on Monday.
Klahn won his first-round match in each of the past two US Open tournaments.
Klahn, ranked 117th this week due primarily to his lack of activity, was forced to withdraw from the Binghamton Challenger before his quarterfinal match against Wayne Odesnik in July.
At the Winston-Salem Open a month later, he reached the round of 32 before losing to John Isner, who, like Klahn, has won the NCAA singles title.
After winning the West Lakes Challenger in Australia in March, Klahn lost his next eight matches, including one to former Menlo School star Dmitry Tursunov at s-Hertogenbosch in The Netherlands, heading into Binghamton.
Klahn and fellow American Tim Smyczek will compete in the men's doubles, taking on Austin Krajicek and John-Patrick Smith in the first round.
He'll also partner with Shelby Rogers in mixed doubles. They meet Alla Kudryavtseva and Aisam-Ul-Hag Qureshi in their opening match.
Stanford products Bob Bryan and Mike Bryan, the top seeds in the men's doubles tournament, open against Max Mirnyi and Mikhail Yoiuzhny.
Tursunov meets Columbia's Alejandro Gonzalez in Tuesday's first-round action and Stanford grad Nicole Gibbs, who earned a wild card into the main draw, plays France's Carolina Garcia in a women's singles first-round match.
Gibbs and USC grad Maria Sanchez will team up in women's doubles. They face Lauren Davis and Renata Voracova in the first round.
Atherton resident Catherine Bellis, who earned a wild card into the main draw, meets 12th-ranked Dominika Cibulkova on Tuesday. Bellis, 15, is the youngest female since Lindsay Davenport in 1991 to play in the US Open.
Bellis is officially ranked 1,211th in the world this week.