She joins Marc Rosset, Roger Federer and Stan Wawrinka in the elite club.

The American won the friendly contest, 6-4, 6-4, over the fellow former US Open champion.

The 27-year-old represented Spain for the second time on the Olympic stage, reaching the women's singles quarterfinals.

The Japanese star has demonstrated a similar steadfastness to the 77-year-old, and thus has earned herself a special place in the legend's heart.

The Aussie provides a brief behind-the-scenes look at the special event. 

He's 10-15 overall against the three greatest men’s players of all time, but even more dangerous in best-of-three format.

Meanwhile, Matteo Berrettini removed himself as a possible candidate for the role. 

The world No. 1 fell to Germany's Alexander Zverev in three sets in Tokyo. 

The Frenchman was trailing Emil Ruusuvuori, 6-4, 4-6, 0-3, in the round of 16 when the heat became unbearable. 

The 20-time Grand Slam champion is the first player ever, male or female, to reach the semis in singles three times.