Fivethirtyeight comments, with Elo ratings to boot.
In his prime, Federer had to beat some great players, including a young Djokovic and Nadal and an older Andre Agassi. But the challenge Djokovic has overcome is more formidable. Since his rise to No. 1 in the official rankings and in our Elo rankings in 2011, he has competed with Nadal and Andy Murray in their primes, and a still-dangerous Federer.
That competition has helped bring Djokovic today to the highest peak of anyone in our data set, edging just ahead of Borg and Federer. Djokovic peaked following his semifinal win at this year’s French Open2, reaching one-tenth of a point higher than Borg reached after his semifinal win at the 1980 U.S. Open. (They both lost the subsequent final.) Djokovic is still within striking distance of that high now. The chart also shows how closely matched he, Federer, Nadal and Murray were in 2010. They were truly a Big Four then, and there was no telling who would be the biggest of them in the subsequent few years. It turned out to be Djokovic.