DEFENDING champion Rafael Nadal’s only trace of a problem during his second-round victory at the U.S. Open was a warning for letting the 25-second serve clock expire.

And Nadal was convinced that even that wasn’t really his fault.

Nadal won 46 of 55 first-serve points and wore down Vasek Pospisil 6-3, 6-4, 6-2 in Arthur Ashe Stadium on Wednesday night.

The serve clocks are making their Grand Slam debut at Flushing Meadows, and folks have been curious to see whether that would have any effect on Nadal, who is known for taking his time between points.

At 2-1 in the final set, he drew a warning from the chair umpire because the 25 seconds ran out.

Nadal was convinced that the only reason that happened was that he paused when Pospisil briefly put a hand up to ask him to wait.

Either way, the 2-hour win was over soon thereafter.

TOP RESULTS —
Serena Williams (USA x17) bt Carina Witthoeft (GER) 6-2, 6-2

Venus Williams (USA x16) bt Camila Giorgi (ITA) 6-4, 7-5

Rafael Nadal (ESP x1) bt Vasek Pospisil (CAN) 6-3, 6-4, 6-2

Fernando Verdasco (ESP x31) bt Andy Murray (GBR) 7-5, 2-6, 6-4, 6-4

Sloane Stephens (USA x3) bt Anhelina Kalinina (UKR) 4-6, 7-5, 6-2

Juan Martín Del Potro (ARG x3) bt Denis Kudla (USA) 6-3, 6-1, 7-6 (7/4)