Naomi Osaka continued her pursuit of a historic gold medal by easing into the third round of the Olympic singles competition at the Ariake Tennis Park.

The Japanese star won her first match in eight weeks against Zheng Saisai on Sunday, saying she felt refreshed and happy after stepping away from the court for mental health reasons.

There were a few understandable signs of rust but Osaka, who is hoping to follow up her starring role at the opening ceremony with a first gold medal for Japan in tennis, was very sharp in a 6-3 6-2 victory over Swiss Wimbledon quarter-finalist Viktorija Golubic on Monday.

The 23-year-old, who has only lost one of her last 24 matches on hard courts, said: "It would mean a lot to win gold here but I know it's a process. I know these are the best players in the world and, honestly, I haven’t played in a while, so I’m trying to take it one notch at a time.

"All in all, I’m just really happy to be here. I haven’t been in Tokyo for a couple of years."

Osaka did not play a match between the first round of the French Open in May and Sunday’s victory but she has shown before she can find her best tennis straight off the bat, going unbeaten between February 2020 and March this year while playing just four tournaments.

"I put this pressure on myself to do well because I know that I don’t play that many tournaments and I feel like I watched these players playing the tournaments while I was on my break so I just really, really want to do well," she said.

"I feel like as long as I work hard, relatively keep my head down, then good things will happen. For me, it’s dream to be here, to play the Olympics. This is my first one, so I’m just trying to cherish this experience."

Men’s gold medal favourite Novak Djokovic also moved into the third round with a 6-4 6-3 victory over Germany’s Jan-Lennard Struff.

The top seed, who is looking to complete an unprecedented Golden Slam in 2021, survived a tight opening to the match to win in straight sets and set up a clash with Spain’s Alejandro Davidovich Fokina.

There were comfortable wins for several big names, with Garbine Muguruza beating Wang Qiang 6-3 6-0, French Open champion Barbora Krejcikova seeing off Leylah Fernandez 6-2 6-4, Alexander Zverev defeating Daniel Elahi Galan 6-2 6-2 and second seed Daniil Medvedev racing to a 6-2 6-1 victory over Sumit Nagal.

But three high seeds did fall in the women’s draw – third seed Aryna Sabalenka of Belarus going down 6-4 3-6 7-6 (7-3) to Croatia’s Donna Vekic while sixth seed Iga Swiatek was beaten 6-3 7-6 (7-4) by Paula Badosa of Spain and Czech flag bearer Petra Kvitova fell in three sets to Belgium’s Alison Van Uytvanck.

Fourth seed Elina Svitolina has had two tough matches so far, the Ukrainian defeating Ajla Tomljanovic 4-6 6-3 6-4, while Karolina Pliskova battled to a 6-3 6-7 (0-7) 6-1 win over Carla Suarez Navarro in the Spaniard’s final Olympic singles match.