The Ultimate Tennis Statistics website, worked up a comprehensive and seemingly bias-free points-based formula to
evaluate annual production. It has Djokovic occupying the top spot (2015) as well as the No. 5 spot (2011). Rod Laver places No. 2 on the strength of his glorious 1969, followed by Roger Federer (2006) at No. 3 and John McEnroe at No. 4 (1984).
....
Federer still holds four of the top eight places, including Nos. 6, 7 and 8 for, respectively, 2007, ‘04, and ‘05). This UTS ranking incorporates many next-level considerations, but the bulk of a player’s points comes from performances in the most important tournaments: the majors, the tour championships and Masters 1000 events.
Given all that, some might still find it surprising, that Djokovic’s 2023 is ranked just No. 15—just behind Andy Murray's 2016 season, in which the Scot finished second in two majors, won Wimbledon and collected an Olympic singles gold. It seems like an anomaly, yet it represents a critical reality about the “best year” debate. First and foremost, it is—or should be—about
domination. It is about the degree of a player’s week-in, week-out, take-no-prisoners, I’m the hammer (and you’re just a nail) consistency. It’s about volume—output, if you prefer.
...