Novak Djokovic’s French Open win makes him a strong chance to clinch the Grand Slam in 2021

For more than 50 years, the Holy Grail of men’s tennis — the calendar year Grand Slam — has remained unattained.

Only Australia’s own Rod Laver has managed the feat in the Open era, and only he and Don Budge have ever completed the set of Australian Open, French Open, Wimbledon and US Open…