Naomi Osaka and Novak Djokovic on track for Tokyo Games gold

Serbian world No 1 aiming to become first man to win all four Grand Slam titles and Olympic gold in the same year

Star tennis players at the Tokyo Olympics continued their march towards the podium with home hope Naomi Osaka easing into the third round on Monday, and men's No 1 Novak Djokovic on track to become the first male player to complete the Golden Slam.

Djokovic defeated Jan-Lennard Struff of Germany 6-4, 6-3 in the men's singles, while aiming to become the first man to win all four Grand Slam titles and Olympic gold in the same year.

The Serb has already won the Australian and French Opens as well as Wimbledon this year. He now needs the Tokyo title and the US Open trophy to complete the collection. Steffi Graf achieved the Golden Slam in 1988.

"It was a tough opponent for a second round... but you know, I'm very pleased with the way I felt on the court," Djokovic said.

And way from the court, Djokovic is enjoying his time in limelight with constant requests for selfies and meetings with competitors from other disciplines.

"It's just so special, you know, it's so special," Djokovic added. "This happens once in four years. Of course, I try to balance things out with keeping my own, you know, routines and things that make me feel good, but I'm thriving also on that wonderful energy."

Djokovic will next face Alejandro Davidovich Fokina of Spain. Davidovich Fokina beat John Millman of Australia 6-4, 6-7 (4), 6-3.

In the women's section, Osaka registered a 6-3, 6-2 victory over Swiss Viktorija Golubic as some of her top competitors bowed out.

World No 3 Aryna Sabalenka of Belarus fell to Donna Vekic 4-6, 6-3, 6-7. Sabalenka's loss came a day after top-ranked Australian Ash Barty's defeat to Spain's Sara Sorribes Tormo.

Two-time Wimbledon champion Petra Kvitova of the Czech Republic was beaten by Belgian Alison van Uytvanck 5-7, 6-3, 6-0, while Iga Swiatek lost to Spaniard Paula Badosa.

It has been an interesting few months for Osaka, who returned to competition this week after pulling out of the French Open over mental health concerns.

Winning Olympic gold on home soil would be perfect for Osaka, but she is not looking too far ahead.

"Well you know, definitely it would mean a lot for me to win gold here but I know it's a process," the world No 2 was quoted as saying by Reuters.

Novak Djokovic of Serbia celebrates winning his men's singles Second Round match against Jan-Lennard Struff of Germany. EPA

"You know, these are the best players in the world and I honestly haven't played in a while so I'm trying to keep it one match at a time. All in all, I'm just really happy to be here."

Meanwhile, fourth seed Alexander Zverev crushed Daniel Elahi Galan of Colombia 6-2, 6-2, while world No 2 Daniil Medvedev enjoyed a comfortable 6-2, 6-1 win over India's Sumit Nagal in the men's division.

The tennis section of the Games reported its first Covid-19 case among participants on Monday after men's doubles players Jean-Julien Rojer of the Netherlands tested positive.

Rojer is the sixth member of the Dutch delegation to test positive after infections reported by a skateboarder, a taekwondo fighter and three members of the rowing team.