WASHINGTON - John Isner hit 17 aces and won 37 of 40 first-serve points Wednesday to move into the third round of the Citi Open by beating Victor Estrella Burgos 6-3, 7-6 (5).

Isner, seeded eighth at the hard-court tuneup for the U.S. Open, never faced a break point, powering serves that regularly topped 130 mph. The American compiled a 26-9 edge in winners.

Isner had his left leg massaged by a trainer late in the second set, then was two points from being pushed to a third when the 51st-ranked Estrella Burgos took a 5-4 lead in the tiebreaker.

But Isner took the final three points — a 139 mph service winner, a 125 mph ace, and then when Estrella Burgos pushed a forehand wide on match point.