Djokovic's body clock gives him time

Only six men in the history of tennis have now won more Grand Slam titles than Novak Djokovic, and as he promised after winning a tenth in New York on Sunday: "As long as there is this flare in me, I will be coming back."

Winning three more Grand Slams would take him past Bjorn Borg, Rod Laver and Roy Emerson on the all-time list, and in sight of Pete Sampras and Rafael Nadal, who both have 14 to their name.

Roger Federer's record of 17 remains the ultimate goal. Djokovic has nearly six years on Federer, but modern history suggests such relentless success will be extremely difficult to sustain into his 30s.

Watching him now, though, makes anything seem possible. Djokovic reached all four of…