Jack Draper has seen his fitness levels questioned often during his young tennis career.
Even heading into the US Open quarter-final with Alex de Minaur, the Aussie was the favourite on the basis of his ability to fight out a five-set match.
But ironically it was the engine of De Minaur that faltered as Draper blitzed the 10th seed 6-3 7-5 6-2 in two hours and eight minutes to reach his first major semi-final.
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Draper's victory wasn't a complete surprise, with the British 25th seed failing to lose a set in his four matches at Flushing Meadows and defeating Carlos Alcaraz at Queens earlier this year.
But the magnitude of the defeat for De Minaur at the hands of Draper had sadly been coming for the Australian all the tournament.
De Minaur was barely able to put up a fight against the left-hander, conceding 20 break points and losing 29 more points than Draper across the three sets.
This time it was De Minaur's body that let him down when his greatest opportunity at a major had been presented to him.
With the likes of Carlos Alcaraz, Stefanos Tsitsipas and Hubert Hurkacz eliminated early in the tournament, De Minaur was the highest-ranked player in his quarter by the third round.
But there was one glaring factor that was 100 percent going to stop De Minaur from contending at the US Open - it was his first tournament since July.
The Australian was forced to pull out of his Wimbledon quarter-final against Novak Djokovic after severely injuring his hip during match point versus Arthur Fils in the previous round.
De Minaur's injury saw him miss the Olympics and the majority of the North American hard court season, which involves Masters tournaments in Montreal and Cincinnati.
This meant De Minaur arrived at Flushing Meadows underdone and with no chance of being a contender at the US Open.
The fact he reached his third consecutive grand slam quarter final in 2024 is an extraordinary achievement considering he wasn't able to play his best tennis often at Flushing Meadows.
De Minaur is still only 25 years old. There will be more grand slam quarter-finals to come for the Australian.