SAN DIEGO (AP)No. 8 seed J.J. Wolf, coming off a third-round run at the U.S. Open, beat fellow American Stefan Kozlov 6-2, 7-6 (6) in the opening round of the San Diego Open ATP 250 on Monday night.

They had faced each other seven times in Challenger and Futures events but this was their first encounter at the tour level.

”I’ve never been seeded before at an ATP tournament, so I’ve got to feel good about it,” said Wolf, 23, who earlier this month stunned 18th-ranked Spaniard Roberto Bautista Agut in straight sets at the U.S. Open. ”I think I’m still getting used to playing night matches. They’re so special. I think I remember everyone I’ve played at night just because of the environment. Everybody is relaxed and having a good time, so I came out in a good mindset.”

Seventh seed James Duckworth claimed an all-Australian battle against Alexei Popyrin, winning, 7-5, 4-6, 6-1 to cap a 2-hour, 17-minute match that he capped with his 14th ace of the afternoon. The 30-year-old improved to 2-0 against Popyrin, having also prevailed last year in the Round of 16 at the ATP Masters 1000 Paris.

Frenchman Constant Lestienne held on to defeat former USC standout Brandon Holt 5-7, 7-6 (5), 6-3, in 2:42. Holt is the son of Hall of Famer Tracy Austin, who watched from courtside.

Tomas Martin Etcheverry was a 7-6 (6), 6-3 winner over countryman Facundo Mena.