Pablo Carreno Busta apologised after he stormed off court and angrily threw his kit bag after losing a five-hour, five-set epic to Japan’s Kei Nishikori at the Australian Open on Monday.

The Spanish 23rd seed said he was “so sorry,” after being booed off when his emotions boiled over following a disputed call in the dying moments of the match.

He was ahead 8-5 in the first-to-10-point deciding game when he became embroiled in a long argument with umpire Thomas Sweeney of Australia after a wrong call of out. He completely lost it after the point was awarded, correctly, to Nishikori who had played a winner despite the bad call, but Carreno Busta thought the point should have been replayed.

The incandescent Spaniard lost the next four points and the fourth-round match and was jeered loudly after launching his kit and racquets towards the exit. It overshadowed marathon man Nishikori’s epic recovery from two sets down to set up a last eight clash against top-ranked Novak Djokovic.

“Obviously I’m very sad, no, because after five hours fighting, after five hours’ match, the way that I leave from the court wasn’t correct, and I’m so sorry, because that’s not me,” Carreno Busta told reporters.

It was never-say-die Nishikori’s third five-setter of the tournament, the second time he came from two sets down and his second triumph via a final set 10-point tie-break, newly introduced for this year’s tournament.

The 6-7 (8/10), 4-6, 7-6 (7/4), 6-4, 7-6 (10/8) win took a draining 305 minutes after an opening set that alone lasted 76 minutes. “I don’t know what to say now. Very tough match. Very great match today,” Nishikori said.

Nishikori had already spent eight hours and 42 minutes on court in his first three matches, including a second-round clash that went the full distance to a final set tiebreak against Ivo Karlovic.

‘It’s not enough’

“I feel it’s not enough,” he joked of his total of spending 827 minutes on court in the first four rounds. “Not easy of course. I try to recover well tomorrow. Today was the longest match I have had this week. I will try to be fresh for the next match.”

Nishikori warmed up for the Australian Open by winning the title at Brisbane and has now reached the quarter-finals for the fourth time in Melbourne without ever going further.

In the first round Nishikori advanced after qualifier Kamil Majchrzak retired due to muscle cramping with the Japanese star leading 3-6, 6-7(6/7), 6-0, 6-2, 3-0 after also dropping the opening two sets. He then beat Karlovic 6-3, 7-6 (7/6), 5-7, 5-7, 7-6 (10/7) and Joao Sousa 7-6 (7/1), 6-1, 6-2.

Nishikori’s seemingly unlimited reserves of stamina have helped him recover from two sets down four times in Slams and he has a win-loss record in five-setters at the Australian Open of 7-1 and 21-6 overall.