MELBOURNE • Roger Federer said the new vulnerability of tennis' "top guys" was good for the sport as he avoided becoming yet another Australian Open casualty last night.
On a day when world No. 1 Andy Murray joined six-time winner Novak Djokovic on the sidelines, Federer advanced to the quarter-finals by claiming the scalp of Japan's world No. 5 Kei Nishikori over five gruelling sets. He will now play Murray's conqueror Mischa Zverev in the last eight.
His 6-7 (4-7), 6-4, 6-1, 4-6, 6-3 victory over Nishikori moves him closer to a surprise 18th Grand Slam title. With no Murray or Djokovic in the draw, his chances have improved greatly and given new belief to the others that they can go on and win the year's first Grand Slam.
With Federer and his long-time Slam rival Rafael Nadal, the final member of tennis' former 'Big Four', rolling back the years, the Swiss maestro said the shock results have been good for the sport.
"I felt like if Rafa and myself can be healthy, yes, you can expect that (they would be in the quarter-finals). That Novak and Andy are not, that is a big surprise," he said.
Men's 4th rd Mischa Zverev (Ger) bt Andy Murray (Gbr) 7-5 5-7 6-2 6-4, Roger Federer (Sui) bt Kei Nishikori (Jpn) 6-7(4) 6-4 6-1 4-6 6-3, Stan Wawrinka (Sui) bt Andreas Seppi (Ita) 7-6(2) 7-6(4) 7-6(4), Jo-Wilfried Tsonga (Fra) bt Daniel Evans (Gbr) 6-7(4) 6-2 6-4 6-4.
Women's 4th rd
Anastasia Pavlyuchenkova (Rus) bt Svetlana Kuznetsova 6-3 6-3, Venus Williams (USA) bt Mona Barthel (Ger) 6-3 7-5, Coco Vandeweghe (USA) bt Angelique Kerber (Ger) 6-2 6-3, Garbine Muguruza (Esp) bt Sorana Cirstea (Rou) 6-2 6-3
"I never thought that Mischa Zverev and Denis Istomin (who beat Djokovic) would beat those two big guys.
"It's good for tennis that a lot of guys believe strongly now that the top guys are beatable, are vulnerable, especially on a faster court."
Nishikori, who had lost his last three matches against Federer, was troubled by a left hip injury and twice needed courtside treatment from a trainer in the match.
"I felt great in the fifth set, I must say. Great energy," Federer said. "Even deep into the fourth I thought, 'Yeah, fifth, here we go, no problem for me. I'm feeling good about my chances'."
Still, he had kind words for Nishikori, noting: "Kei's a tough customer. This is a huge win for me in my career.
"Kei will give you some looks, he's not the biggest server on tour but one of the greatest on the baseline."
The Swiss holds a career 2-0 record over German Zverev. "I would never have picked it, I like Mischa a lot and he has a nice game coming forward. It will be different," the four-time Australian Open winner said.
The Swiss is looking to become the third man to win five Australian Open singles titles after Djokovic and Roy Emerson, who have both won six. It is the 13th time Federer has reached the last eight, extending his record for most Australian Open quarter-finals.