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After six months out of the game, Federer's fairytale return continued under the lights of Rod Laver Arena where he emphatically quashed doubts about his fitness in three hours and 24 minutes of high-octane tennis.
Having stormed into the match after a 90-minute demolition of Tomas Berdych, Federer showed his appetite for a grind, going toe-to-toe with the fleet-footed Japanese in a match of marathon points.
He sealed the match with an imperious smash down the line and will play Mischa Zverev for a place in the semi-finals.