Isner, the tournament's top seed and two-time champion, served 17 aces and needed just 68 minutes to oust the 13th-seeded Kukushkin.
WINSTON-SALEM, N.C. -- American John Isner made short work of his third-round match Wednesday in the Winston-Salem Open, beating Kazakhstan's Mikhail Kukushkin 6-1, 7-6 (7-3).
Isner, the tournament's top seed and two-time champion, served 17 aces and needed just 68 minutes to oust the 13th-seeded Kukushkin in the final tuneup for next week's U.S. Open.
Isner, 12-0 all-time in the tournament, will face seventh-seeded Lukas Rosol of the Czech Republic in Thursday's semifinals. Rosol advanced with a 1-6, 6-2, 6-2 victory over 10th-seeded Pedro Andujar of Spain.
Also advancing to the quarterfinals were American Sam Querrey, fifth-seeded Guillermo Garcia-Lopez of Spain, Belgian qualifier David Goffin, Poland's Jerzy Janowicz, ninth-seeded Yen-Hsun Lu of Taiwan and 14th-seeded Andreas Seppi of Italy.
Querrey will play Garcia-Lopez in one quarterfinal match at the Wake Forest Tennis Center. The other pairings have Goffin facing Janowicz and Lu taking on Seppi.