By Ian Ransom
MELBOURNE (Reuters) - Roger Federer showed his 35-year-old legs may yet still carry him to a long-awaited 18th grand slam title as he overhauled fifth seed Kei Nishikori in a five-set slog to reach the Australian Open quarter-finals on Sunday.
Having issued a reminder of his class in the 90-minute rout of Tomas Berdych, Federer flaunted his endurance by prevailing 6-7(4) 6-4 6-1 4-6 6-3 after a three hour and 26 minute battle under the lights at Rod Laver Arena.
After six months out of the game to recover from a knee injury, Federer's fairytale return will continue against giant-killing German Mischa Zverev, who sensationally ousted top seed Andy Murray on the same centre court only hours before.
Since winning Wimbledon in 2012, Federer has gone close to adding to his major tally, but with each passing year, the doubts have only piled higher.
Yet with Murray and six-times Australian Open champion Novak Djokovic sent packing from Melbourne Park, the Swiss master finds himself with his best chance in years and revelled in his physical condition when taken deep by Nishikori.
"I felt great in the fifth (set), I must say," the 17th seed told reporters. "Great energy. Even deep into the fourth I thought, 'Yeah, fifth, here we go, no problem for me'.
"I'm feeling good about my chances.
"But tonight was special, no doubt about it. Going five against Kei here on Rod Laver Arena with the comeback, it's definitely very special."
The match threatened for a time to be anything but special as Asia's first men's grand slam finalist stormed to a 4-0 lead before weathering a huge Federer recovery to take the first set on a tiebreak.
The Swiss hit back quickly, belting a huge return to break Nishikori in the seventh game of the second.
Federer served out the set to love when Nishikori hit a return into the tramlines and the old master threw a steely gaze at his player's box, pumping his fist.
Rattled by the pressure, Nishikori became twitchy, his fidgeting between points betraying the nerves as Federer roared through the third set in 26 minutes.
The Swiss looked to be coasting to victory but he suffered a rare wobble at 2-2 in the fourth, shanking a straightforward smash and then netting a volley to give up two break points.
The door ajar, Nishikori barged through it with a stinging passing shot as Federer rushed the net with more hope than design.
Nishikori served out to love, the match back to level terms as Federer's suddenly misbehaving backhand saw him put a return just wide of the line.
Nishikori took a medical time-out between sets, with a trainer working hard on his legs, but it was Federer who appeared in greater need of a massage as he was thrown around the court by the Japanese.
But the Swiss held on grimly, and grabbed his chance in the second game when Nishikori netted to offer two break points.
The Japanese saved the first and fired a huge serve on the next that should have settled the argument. But Federer somehow made the return with a desperate backhand lunge.
Nishikori came in for the kill with an open court spread before him but dumped the ball into the net, triggering thunderous cheers from a crowd heavily favouring the Swiss.
From there, Federer rode the momentum to the finish, serving out the match strongly and savouring another huge ovation after having defied father time once again.
(Editing by Sudipto Ganguly and Ken Ferris)