CINCINNATI (AFP) – Carlos Alcaraz won the ATP Cincinnati Open title on Monday after defending champion Jannik Sinner retired due to illness in the first set.

World No. 1 Sinner came into the final feeling unwell and lost the first seven points of the match before throwing in the towel at 5-0 down in a game played in 30-degree Celsius heat.

Sinner will now focus on recovery with the US Open starting on Sunday. The Italian is due to take part in the US Open's revamped mixed doubles on Tuesday, but his participation in that draw is now in serious doubt.

"I'm disappointed, I didn't feel great from yesterday," Sinner said afterwards.

"During the night, I thought I would recover a bit better, but it was not the case.”

"I just tried to go out for the fans, trying to give (them) a match - that's the reason why I went on the court.”

"But it was not meant to be for me today. But I don't want to take anything away from Carlos. He had a great week, great, great tournament again."

Sinner said he is now pointing to the final Grand Slam of the season.

"The main focus, obviously, is for the US Open. Recovery is the most important. And then we see," he said.

Despite the temporary health setback, Sinner is pleased with his showings in 2025.

"I feel like it's an incredible season," he said.

"We'll keep going, keep pushing. I have some points to improve if I want to go far in US Open.”

"It was a good test this week, trying to understand where my level is."

Sinner lasted for just 22 minutes, calling for the doctor after losing the fifth game and shortly after going to shake hands with Alcaraz.

It was the second match in a row Alcaraz had won over an ailing opponent, following his win over Alexander Zverev in the semifinals.

Alcaraz won his 22nd career title as he claimed his 17th victory in a row at the Masters 1000 level.

He now leads Sinner 9-5 and lost to the Italian in their last match, the Wimbledon final last month.