Grand Slam King Djokovic has captured 100 career championships, held the world No. 1 ranking a record 428 weeks and has finished as year-end No. 1 a record eight times.

The former skier turned tennis champion knows all about navigating the peaks and valleys of the pro tour and is in a unique position to assess tennis’ most monumental milestones.

Speaking to the media after his US Open second-round win today, Djokovic cited two achievements as most massive milestones in tennis: attaining world No. 1 and achieving the career Golden Slam.

Only five singles champion in history—Andre Agassi, Steffi Graf, Serena Williams, Rafael Nadal and reigning Olympic gold-medal champion Djokovic—have won the career Golden Grand Slam collecting all four major championships plus the Olympic gold medal.

The 24-time Grand Slam champion Djokovic said the career Golden Grand Slam and world No. 1 ranking are the two paramount achievements in tennis.

“I would say probably the top two things would be, yeah, winning the Career Slam or Golden Slam, including the golden medal at the Olympics, and staying No. 1 for many years,” Djokovic said after his 6-7(5), 6-3, 6-3, 6-1 win over American Zachary Svajda on Ashe Stadium. “Because, you know, slams are such a big goal of every single player, and they take a lot of energy to be conquered.

“So for you to be consistently playing well over and over again, to be a contender for No. 1 in the world, that’s probably one of, if not the ultimate challenge.

“Because it requires a 24/7 attention to every single detail when it comes to physical recovery, preparation, mental training, anything really that revolves around an individual athlete, because in the end of the day, you have to do the job yourself on the court.”

Applying Djokovic’s Golden Slam standard, you can make a case Steffi Graf owns one of the most impressive records in tennis history. Graf stands alone as the only player to win the single-season Golden Slam—capturing all four Grand Slam crowns and the Olympic gold medal—a feat she achieved in 1988 when the Seoul Olympics were played in September after the US Open. That required Graf to win in New York City in early September then fly to Korea to strike gold after completing the calendar Grand Slam.

While Djokovic’s rival, Rafael Nadal, won Olympic gold in both singles and doubles, Serena Williams is the only player to achieve the career Golden Slam in both singles and doubles. Serena Williams partnered sister Venus Williams to Olympic gold in doubles in 2000 (when Venus Williams won singles gold as well), 2008 and 2012 when Serena Williams struck gold in singles and doubles at the London Olympics.

Of course, Djokovic very nearly pulled off the calendar Slam in 2021 when he won Australian Open, Wimbledon and Roland Garros then reached the Flushing Meadows final where Daniil Medvedev denied his calendar Grand Slam dream.