Britain's Kyle Edmund was hampered by injury as he lost in five sets to world number 81 Damir Dzumhur in the first round of the Australian Open.
Edmund twice led by a set in baking hot conditions at Melbourne Park but a problem with his left leg helped Dzumhur fight back to win 1-6 7-6 (7/4) 4-6 6-3 6-1.
The British number three first called the trainer after the seventh game in the third set and while he managed to serve out for a 2-1 lead, it was one-way traffic thereafter.
With temperatures reaching 33 degrees Celsius, Edmund admitted before the match he had little experience of five-setters in sweltering heat but this appeared a muscular deficiency, rather than one of stamina.
The talented youngster from Yorkshire, ranked 88th in the world, was able to demonstrate his impressive striking ability during a glorious first set but, despite noticeable physical improvements in recent months, his body is yet to fully mature.
The 21-year-old pulled out of the French Open third round last year with a separate stomach injury, which then curtailed his preparations for Wimbledon, where he lost in the first round.
Edmund's potential, however, is not in doubt and he played like a dream in a 26-minute opening set, driving his forehand into the corners and breaking twice for the loss of just one game.
If the Briton was hoping for a swift work-out, however, he would soon be disappointed as Dzumhur found his rhythm to seize an early break in the second after Edmund dropped a backhand into the net.
Edmund was temporarily rattled as he shanked a simple smash and while he fought back to force a tie-break, Dzumhur held his nerve to level at one set all.
Rediscovering his groove, Edmund broke early in the third but his momentum was halted at 4-3, as he called on the trainer to massage a problem with what looked like his left hip.
After a lengthy delay, he served out the set, but the pain was clearly still causing trouble as the trainer again gave him treatment at the change of ends.
Whether the greater effect was physical or psychological, Edmund lost his way in the fourth, hardly winning a point on his opponent's serve and twice losing his own as Dzumhur cruised into the decider.
Now it was the Bosnian who could smell victory as Edmund, wincing and clutching his thigh, gave away five break points at 1-1 before succumbing on the last to hand his opponent the decisive advantage.
Dzumhur never looked back, storming into a 5-1 lead, and as Edmund could barely make it to the baseline to serve his final game, a backhand into the net confirmed defeat in three hours and 12 minutes.