World No. 1 Novak Djokovic opened his mission to win tennis' Golden Slam, defeating Hugo Dellien of Bolivia 6-2, 6-2 on Saturday in the first round of play in the 2020 Tokyo Olympics.

Djokovic needs to win the U.S. Open in September to complete the Grand Slam -- and an Olympic gold medal would make him the first man to achieve the Golden Slam. On the women's side, Steffi Graf of Germany did it in 1988.

Next up for the Serbian will be Jan-Lennard Struff of Germany, who beat Thiago Monteiro of Brazil 6-3, 6-4.

Daniil Medvedev, the world No. 2, made his Olympic debut with a 6-4, 7-6 (8) victory against Alexander Bublik of Kazakhstan. Also advancing were Sumit Nagal of India, the next challenger for Medvedev; Aslan Karatsev, like Medvedev competing for the ROC (Russian) squad; France's Jeremy Chardy and Ugo Humbert; Alejandro Davidovich Fokina and Pablo Carreno-Busta of Spain; Australian John Millman; Italians Lorenzo Sonego and Fabio Fognini; and Marin Cilic of Croatia.

Plava Laguna Croatia Open Umag

Carlos Alcaraz of Spain became the youngest finalist of an ATP event in 13 years when he defeated top seed and fellow countryman Albert Ramos-Vinolas 6-2, 7-6 (3) in the seminfnals at Umag, Croatia.

The 18-year-old Alcaraz came out on top in the grueling three-hour, 37-minute duel and matched Kei Nishokori of Japan, who won at Delray Beach in 2008 when he was 18.

Alcaraz will try to match Nishokori's title feat when he faces Richard Gasquet of France, who was once ranked as high as No. 7. Gasquet, the No. 4 seed, defeated qualifier Daniel Altmaier of Germany 7-6 (2), 3-6, 6-3 in the other semifinal.

Swiss Open

Hugo Gaston of France came from behind to defeat No. 7 seed Laslo Djere of Serbia 3-6, 6-3, 6-3 to reach the final in Gstaad.

Prior to this week, Gaston never had made it past the second round at an ATP Tour event. Djere, on the other hand, was seeking his second final of the season.

Gaston will face No. 3 seed Casper Ruud of Norway in the final on Sunday. Ruud defeated Czech qualifier Vit Kopriva 6-3, 6-0 to reach his second straight ATP Tour final. He won the Nordea Open last week.