"I have to be happy that I didn't lose today", added the Japanese, who missed the Australian Open past year due to a wrist injury.
There, he had a colossal chance to score the win, creating three break points at 4-4 that Kei successfully defended to survive and reach the match tie break that he claimed 10-7 to cross the finish line first and secure the place in the last 32.
Despite the massive deficit on serve - Karlovic rocketed 59 aces to Nishikori's nine - the Japanese appeared to have rounded into better form than he displayed in his narrow first-round victory over Polish qualifier Kamil Majchrzak, who retired with injuries midway through the fifth set Tuesday.
The U.S. Open champion defeated the unseeded Slovenian 6-2, 6-4 to set up an all-Asian clash with Hsieh Su-wei of Taiwan in the next round.
A first-round win made him the oldest man to win a match at the Australian Open since Ken Rosewall in 1978.
"It feels like 4 hours passed by in about 15 minutes".
He launched his campaign for a seventh with a 6-3, 6-2, 6-2 victory over Mitchell Krueger, a 25-year-old American making his debut in the main draw here. It's good to see him playing well.
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But Ms Lucas said the PM was refusing to take the possibility of "no deal" off the table and was reluctant to extend Article 50. However Mr Mundell also excluded "arrangements that seek to stop Brexit", including a People's Vote.
After dropping serve twice in the first set against Brengle, Pliskova completely dominated the second and third sets and capped it with a pair of aces. He was smiling, but no one knew for sure if he was offended or was just joking.
"I had a lot of ups and downs in 2018, and I'm trying to fix parts of my game", Chung said.
The 23-year-old Majchrzak then went on to close out his next two service games and the set without being seriously threatened.
Among other Japanese players, Taro Daniel lost 6-3, 7-6 (2), 6-3 to Canadian 25th seed Denis Shapovalov. Tsonga, who has had his own fitness issues in recent years and is now ranked No 177 in the world, beat Martin Klizan 6-4, 6-4, 7-6.
Nishikori had to dig himself out of a 0-40 hole at 4-4 in the fifth set, and the match went to yet another tiebreaker from which he prevailed by winning the final four points.
Raonic moves on to face Pierre-Hugues Herbert, who scored a 6-2, 1-6, 6-2, 6-4 victory over South Korea's Hyeon Chung, a semifinalist previous year.
She'll next play No. 27 Camila Giorgi, who beat Iga Swiatek 6-2, 6-0. But the game turned quickly as Majchrzak began to suffer cramps in his legs and hands and lost the third set before retiring in the fourth. On Rod Laver Arena, 16th seed Raonic emerged the victor against Wawrinka, a three-time Grand Slam champion who is on the comeback trail from injury.
Later, world number one Novak Djokovic will square off with Wilfried Tsonga of France to advance further in the competition.