Fatigued Djokovic faces heat-prone Sinner at Wimbledon

Novak Djokovic will play Jannik Sinner in the Wimbledon semi-finals on Friday. The clash pits a 39-year-old Serb battling visible physical decline against a 24-year-old Italian top seed whose own body has repeatedly betrayed him in the heat.

Djokovic has reached the latter stages by relying on his aura, immense defence and sheer will to win. In his quarter-final, the 24-time Grand Slam champion required early treatment on his left calf before surviving a record-breaking 5hr 15min epic against Canada's Felix Auger-Aliassime. The 25-year-old third seed squandered a first set he should have won, losing the tie-break 10-12, before producing a poor performance in the decisive 10-point fifth-set tie-break.

This vulnerability has been a repetitive theme for Djokovic throughout the tournament. Against Frenchman Arthur Rinderknech, he lost the third set 6-1 but produced what he called a "perfect" tie-break to avoid a fifth set. Against world No 132 Roman Safiullin, Djokovic was outplayed in a 6-3 third-set loss, though his opponent failed to serve out the first set and could not capitalise thereafter.

Had Djokovic faced a fully fit Carlos Alcaraz or Alexander Zverev in the quarter-finals instead of Auger-Aliassime, the veteran might well be out of the draw. A Wimbledon title would end a drought of 11 consecutive Grand Slams without a trophy. Djokovic has not ruled out this being his final year, adding a potential farewell narrative to his run.

Sinner enters as the favourite if he performs to his capabilities, having defeated Djokovic in the Australian Open semi-finals in January. The world number one is simply too mobile, dynamic and powerful for the current version of the Serb.

Yet Sinner brings his own significant doubts. At the French Open in May, the Italian suffered cramp and dizziness in 32C heat while leading Juan Manuel Cerundolo 6-3 6-2 5-1. He lost 15 points in a row, with courtside microphones capturing him saying he felt dizzy and nauseous. He ultimately lost in five sets, bending over in exhaustion and resorting to drop shots to shorten points.

Such a collapse raises mental questions, as Alcaraz famously beat Zverev in January's Australian Open semi-finals while practically on one leg. Sinner, meanwhile, very nearly exited the Australian Open due to cramps before a roof closure saved him, and he withdrew from a Shanghai Masters match last October due to heat exhaustion. With temperatures at Wimbledon exceeding 32C on Thursday, the semi-final may be decided less by talent than by which player's body holds up under the London sun.