Clinical Karlovic dumps out Lopez

Ivo Karlovic cracked 19 aces past Feliciano Lopez as he knocked the second seed out of the US National Indoor Tennis Championships.

The 34-year-old Croatian was at his punishing best on serve, dropping only six games on his own delivery in a 7-6 (7/2) 6-4 victory over Spaniard Lopez that earned him a quarter-final shot at American Jack Sock.

Australian third seed Lleyton Hewitt recovered from a slow start to beat Marcos Baghdatis of Cyprus 1-6 6-2 6-0.

Fourth seed Lu Yen-hsun fought back from a set down to progress to the quarter-finals. Home qualifier Denis Kudla took the first set of their last-16 contest but the world number 54 from Chinese Taipei came storming back to take the match 3-6 6-3 6-3.

There was better news for another American qualifier as Alex Kuznetsov overcame Kazakh eighth seed Mikhail Kukushkin.

Kuznetsov lost the first set but claimed the second comfortably before snatching the third on a tie-break to seal a 2-6 6-3 7-6 (7/1) victory.