A very animated Roger Federer was understandably delighted when he got the better of the 5th seed, Kei Nishikori in five sets on the Rod Laver Arena this evening.
Federer, a former four-time Australian Open champion, who spent the past six months on the sideline due to a knee injury, soon found himself 0-4 down in the first set, but managed to fight his way back to force a tie-break, which Nishikori went on to win.
Federer then dominated the next two sets and looked to finish it off in the fourth, but Nishikori hung on to force the decider.
Nishikori, who received on-court treatment for what appeared to be an on-going hip injury, was just not strong enough to stop Federer, who went on to win 6-7(4), 6-4 6-1 4-6 6-3.
Federer will now do battle against Mischa Zverev, who ousted the top seed, Andy Murray earlier today.