Djokovic falls in Cincinnati heat in first match since Wimbledon

Thiago Agustin Tirante has rallied past Novak Djokovic 2-6 6-4 6-4 at the Cincinnati Open on Saturday, as the Serbian struggled in the heat and required a medical timeout in a disappointing US Open tune-up.

Playing his first match since his Wimbledon semi-final defeat by Jannik Sinner, Djokovic swept through the opening set of the second-round match before the stifling humidity began to affect him early in the second.

The 39-year-old dropped to his knees during an 18-minute third game that featured nine deuces and 24 points. He received treatment to help cool him down after holding serve.

Djokovic offered little resistance on return for the rest of the set, seemingly focused on reaching the decider, and emerged from the locker room for the third in a change of clothes, looking sharper.

But with the pair level at 4-4, Djokovic made a string of uncharacteristic errors, ending with a volley into the net that gave Tirante the decisive break.

The 50th-ranked Argentine served out the match to secure the biggest win of his career and set up a third-round meeting with Spain's Martin Landaluce.

"I'm thinking about my family and my friends who are in Argentina right now," he said.

"They are in Argentina, but they are in my heart as well."

Djokovic will look to regroup before the US Open, where he will seek a record-extending 25th Grand Slam singles title.