Nishikori rallied after dropping the first two sets and had a chance to serve out at 5-4 in the fifth but was broken. Nishikori, who eventually won 6-7 (8), 4-6, 7-6 (4), 6-4, 7-6 (8), was trailing 8-5 in the tiebreaker when a contentious call changed the momentum and prompted the angry response from Carreno Busta.
Carreno Busta's shot clipped the net, and Nishikori reset to hit a backhand down the line after the ball landed near the doubles alley.
A line judge called it out as Nishikori hit the ball down the line, and Carreno Busta was nowhere close to playing it. He challenged the decision, and Hawk-Eye showed the ball hitting the line, but the point remained with Nishikori.
After arguing with umpire Thomas Sweeney, Carreno Busta lost the next three points and Nishikori sealed the match with an ace. After shaking hands with Nishikori, Carreno Busta threw his bag into the court before collecting it and yelling at the chair umpire as he left the arena.
Carreno Busta in tears in his press conference, apologises for screaming at the umpire: "Obviously I'm very sad because after five hours fighting, the way that I leave from the court wasn't correct, and I'm so sorry, because that's not me."— Eleanor Crooks (@EleanorcrooksPA) January 21, 2019
After spending 5 hours, 5 minutes on court in the fourth round, Nishikori will next play six-time Australian Open champion.
It was the second time in four rounds Nishikori has had to come back after losing the first two sets.
It was also the second time Nishikori has had to win a fifth-set, first-to-10 super tiebreaker, which was introduced at the Australian Open for the first time this year.
Nishikori withstood 59 aces from 39-year-old Ivo Karlovic in his second-round match before winning it in fifth-set tiebreaker.
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