Serena Williams today powered into the fourth round of the Australian Open, defeating Ukrainian Dayana Yastremska. Williams won 6-2, 6-1 in one hour and seven minutes. 

The 37-year-old Williams is chasing a record eighth Melbourne title. She will face either Romanian world number one Simona Halep or sister Venus Williams in the fourth round.

In men's singles, Novak Djokovic defeated Denis Shapovalov 6-3, 6-4, 4-6, 6-0 to reach the Australian Open last 16. Djokovic will face 22-year-old Russian Daniil Medvedev in the fourth round. Medvedev, who cruised into the last 16 of a Grand Slam for the first time, beat Belgian David Goffin 6-2, 7-6, 6-3. 

Meanwhile, Japanese Kei Nishikori was back to his best in a straight-sets victory over Joao Sousa. Nishikori, taken to five sets in his previous two rounds, made it much easier for himself this time with a 7-6, 6-1, 6-2 win over the Portuguese player.