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Novak Djokovic revealed he is battling a 'condition' after falling to his knees in apparent struggle during his shock defeat by Thiago Agustin Tirante.

The tennis great lost 2-6, 6-4, 6-4 on Saturday in a match that took two hours, 44 minutes in hot and humid conditions at the Cincinnati Open, and sparked concerns after the game.

'It's just a condition that I have, health-wise, that has been bothering me for the past couple of years,' Djokovic said after being questioned on his health. 'A lot of issues, especially when it is humid and it is hot.

'I did anticipate it (would be humid), but there are all these things, like nerves and everything involved that make it worse, and that's what happened.'

Djokovic, 39, appeared to struggle physically in the heat and had his 10-match winning streak in Cincinnati snapped.

He has had plenty of success in Cincinnati, with a 45-13 record and titles in 2018, 2020 and 2023. But he wasn't sure he would return.

Novak Djokovic hinted at an unknown health condition follow his defeat at the Cincinnati Open

The tennis great admitted he is unsure if he will ever return to the tournament after the loss

'I certainly hope so, but it looks more likely not, unfortunately,' Djokovic said. 'But let's see what the future brings.'

A 25-year-old from Argentina, Tirante is ranked No50 in the world. Djokovic – a three-time Cincinnati champion and No5 in the rankings – was playing for the first time since his loss to top-ranked Jannik Sinner in the semifinals at Wimbledon.

Up next for Djokovic is the US Open, which starts August 30 in New York.

Djokovic saved 13 of the 15 break points he faced. Tirante broke Djokovic's serve in the ninth game of the final set and then served it out.

'I think this is the best win of my career,' Tirante said. 'I think I really did a good job inside the court. I managed very well the nerves of playing against a legend like Novak.'

In a rain-delayed match that ended at 2.15am Sunday, top-seeded Alexander Zverev rallied to avoid a third straight loss, beating Cameron Norrie 3-6, 6-3, 6-3. After losing to Jannik Sinner in the Wimbledon final, Zverev – the French Open champion – returned to play in Montreal and fell to Tallon Griekspoor in his opener Aug. 5.

On the women's side, Alexandra Eala of the Philippines continued her run of strong play with a victory over Elena-Gabriela Ruse, who lost the first set and stopped playing in the second with an ankle injury. Eala – who is No20 in the rankings - won her first WTA singles title in Washington earlier this month and has won eight of her last nine matches.

American Jessica Pegula beat Simona Waltert 6-3, 6-2, improving her record to 25-6 on hard courts in 2026. The third-ranked Pegula won the title in Cincinnati in 2024.