Nishikori won the longest match of the tournament so far in a deciding fifth-set tie-break against Spaniard Pablo Carreno Busta.
The Spaniard then showed his discontent after a line decision didn't go his way, and the incident appeared to rattle him as Nishikori completed the win with an ace, meaning he has come back from two sets down for the second time this tournament.
After being two points from victory, Carreno Busta lost five straight, including that one in the last tiebreaker where he berated the chair umpire for not ruling a replay, allowing Nishikori to advance 6-7 (8), 4-6, 7-6 (4), 6-4, 7-6 (8).
Carreno Busta left the court screaming at the umpire after feeling the point at 8-5, when his shot was erroneously called out, should have been replayed.
He stormed over to his bag, to the boos of the crowd on Margaret Court Arena, as he turned back towards the chair umpire and screamed at the top of his lungs.
Two legends of Australian tennis have suggested Pablo Carreno Busta was right to blow up at the umpire after his controversial loss.
The pair shook hands after the match.
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The chair umpire awarded a point to Nishikori in the 5th set tiebreak when the Japanese was 5-8 down. However, Nishikori didn't lose his cool and broke Carreno Busta once again and held his serve thereon to take the match into the fifth set.
On the disputed 14th point, Carreno Busta's shot clipped the net and bounced on the left line.
The crowd was as appreciative of the fight Carreno Busta put up but Nishikori used all his experience and huge hitting ability to push through. Today was the toughest match.
However a number of tennis pundits have come out in support of Carreno Busta and explained why the umpire got the call wrong. If I call the Hawk-Eye and the ball is out, I lost the Hawk-Eye. He gave a great match today.
"I feel like it's not enough", Nishikori joked courtside when reminded that he had spent 13 hours and 47 minutes on court in the first four rounds.
"But I think that the referee missed - the umpire who is near the court missed, and, well, I try to leave [as] fast as possible when I lost that last point, because I know that in any moment I lost the head", The Age reported he said.