Related video above: Novak Djokovic shows off trophy after Australian Open winNovak Djokovic’s bid for a "Golden Slam" is alive and well following a routine 6-2, 6-2 win over 139th-ranked Hugo Dellien of Bolivia in the opening round of the Tokyo tennis tournament. The Tokyo Games mark Djokovic’s fourth consecutive Olympic appearance. He lost in an upset during the 2016 Olympic Games in Rio to Juan Martin Del Potro in the first round of the tournament. The top-ranked Serb is attempting to become the first man to win all four major tennis tournaments and an Olympic singles gold medal in the same year. He's already won the French Open, Australian Open and Wimbledon this year. He still needs to take gold in the Olympics and win in the U.S. Open later this summer to complete the Golden Slam. Steffi Graf was the only tennis player to accomplish the Golden Slam in 1988.Djokovic’s next opponent will be 48th-ranked Jan-Lennard Struff of Germany.Struff eliminated Thiago Monteiro of Brazil 6-3, 6-4.