MELBOURNE, Australia -- Novak Djokovic extended his Grand Slam winning streak against lefthanders with a 6-3, 6-4, 4-6, 6-0 win over Denis Shapovalov on Saturday in the third round of the Australian Open.
The win guaranteed that Djokovic would keep his No. 1 ranking after the Australian Open. Rafael Nadal could have taken the top ranking if he won the tournament and Djokovic lost before the fourth round.
Djokovic has won 18 consecutive matches against lefties since being beaten by Nadal in the French Open final in 2014. Overall, Djokovic has a 32-11 record against lefthanders in majors.
Djokovic will next play No. 15 Daniil Medvedev, who defeated No. 21 David Goffin 6-2, 7-6 (3), 6-3.
In other men's third-round matches, Kei Nishikori scored a straight-sets victory over Joao Sousa, getting a bit of relief after his first two matches in the tournament went to five sets.
Nishikori, the No. 8 seed, had a 7-6 (6), 6-1, 6-2 win at Margaret Court Arena. He fended off 59 aces from 39-year-old Ivo Karlovic in the second round before winning the fifth-set tiebreaker 10-7.
It was Nishikori's third straight game at Margaret Court Arena, and he said he enjoyed the vibe.
"Forehand has been working very well," Nishikori said. "Second and third sets I was playing really aggressive, and everything was working well."
Nishikori, the 2014 US Open finalist, has reached the fourth round in Australia for the seventh time and is on a roll after winning the season-opening tournament in Brisbane.
Nishikori moves on to face No. 23 Pablo Carreno Busta, who upset No. 12 Fabio Fognini 6-2, 6-4, 2-6, 6-4 later in the day.
Milos Raonic, the No. 16 seed, eased to a 6-4, 6-4, 7-6 (6) win over Pierre-Hugues Herbert to move into the fourth round of the Australian Open for the sixth time. Raonic swept to 3-0 and 5-1 leads in the tiebreaker, but Herbert rallied to level at 5-5. Herbert saved one match point before Raonic clinched the 2-hour, 1-minute match with an ace.
Raonic will play the winner of the later match between No. 4 Alexander Zverev and Alex Bolt.
The Associated Press contributed to this report.