Sock, Monaco reach the U.S. Men's Clay Court final

Fourth-seeded defending champion Jack Sock beat top-seeded John Isner 7-6 (4), 6-3 on Saturday in an all-American semifinal in the U.S. Men's Clay Court Championshi at Houston.

Sock will face Argentina's Juan Monaco in the final Sunday at River Oaks. The 23-year-old American has won 16 consecutive sets in the event dating to his first-round match last year.

"I love playing in this city, on this court. I love the clay," Sock said.

The 32-year-old Monaco, the 2012 winner, beat third-seeded Feliciano Lopez of Spain 6-4, 6-2.

American twins Bob and Mike Bryan won the doubles titles for the sixth time, beating Victor Estrella Burgos of the Dominican Republic and Santiago Gonzalez of Mexico 4-6, 6-3, 10-8. The Bryans have 110 team titles.

• Australian Open champion Angelique Kerber, ranked No. 2 in the world, retired because of a viral illness during her semifinal match at the Volvo Car Open in Charleston, S.C., sending American Sloane Stephens to the final.

Stephens will face Elena Vesnina, the Russian qualifier who upset fifth-seeded Sara Errani of Italy 6-4, 4-6, 6-2 in the other semifinal.

Vesnina, who reached the final in Charleston five years ago before losing to Caroline Wozniacki, is first qualifier to make the finals in the 44-year history of the tournament that started on Hilton Head Island.

Stephens won the first set 6-1 and was leading 3-0 in the second when Kerber, the top seed in the tournament, retired. A trainer came to court to examine Kerber after the second game of the set. She returned to the court, but won only one point in the third game before retiring.