Wawrinka into quarter-finals

New York - Australian Open champion Stanislas Wawrinka powered into the quarter-finals of the US Open on Monday with a 7-5, 4-6, 7-6 (9/7), 6-2 victory over Tommy Robredo.

The third-seeded Swiss fired 18 aces, saving two set points in the third-set tiebreaker and dominating the fourth set against the 16th-seeded Spaniard.

Wawrinka fired 75 winners, including 27 in the third set that surpassed Robredo's total of 19 for the match.

"It was a really tough battle today," said Wawrinka, who also survived a tumble into the courtside seats in Armstrong Stadium when he hit the knee-high board surrounding the court at full stretch for a shot.

"I had some ups and downs physically," he said. "From that I'm OK, I'm more tired from the running, from the match.

"When you win, it's always more easy to feel good after," added Wawrinka, who had won only two of his prior eight matches against Robredo.

One of those victories was in the fourth round of the Australian Open en route to his first Grand Slam title.

Wawrinka will next face Kei Nishikori of Japan, who beat fifth-seeded Milos Raonic of Canada 4-6, 7-6 (7/4), 6-7 (6/8), 7-5, 6-4 in the late match.

Results on Monday from the eighth day of the US Open, the final Grand Slam tournament of 2014 (x denotes seeded player):

Men

Fourth round

Novak Djokovic (SRB x1) bt Philipp Kohlschreiber (GER x22) 6-1, 7-5, 6-4
Andy Murray (GBR x8) bt Jo-Wilfried Tsonga (FRA x9) 7-5, 7-5, 6-4
Stanislas Wawrinka (SUI x3) bt Tommy Robredo (ESP x16) 7-5, 4-6, 7-6 (9/7), 6-2
Kei Nishikori (JPN x10) bt Milos Raonic (CAN x5) 4-6, 7-6 (7/4), 6-7 (6/8), 7-5, 6-4

Women

Fourth round

Serena Williams (USA x1) bt Kaia Kanepi (EST) 6-3, 6-3
Flavia Pennetta (ITA x11) bt Casey Dellacqua (AUS x29) 7-5, 6-2
Victoria Azarenka (BLR x16) bt Aleksandra Krunic (SRB) 4-6, 6-4, 6-4
Ekaterina Makarova (RUS x17) bt Eugenie Bouchard (CAN x7) 7-6 (7/2), 6-4