Second-ranked Zverev battles illness ahead of Shanghai Masters after missing Beijing

The world number two admitted that his illness would take a few months to clear completely but that he would play on until the end of the 2024 season, starting with this week's Shanghai Masters .

"I was physically struggling, I was not healthy. I didn't know what it was," the 27-year-old German told reporters in Shanghai.

"I still have a feeling of maybe being a bit more tired than I'm used to.

"But it's either I'm going to take the whole season off now or I'm going to play the way I can play."

Zverev is one of a number of players who have raised concerns about the packed ATP Tour calendar and its effects on health.

"The ATP doesn't care about our opinion - it's a money business," he said last month.

Zverev won the Italian Open this year and reached the French Open final where he lost to Carlos Alcaraz.

But he described his performance at the US Open as "absolutely terrible" after losing in the quarter-final to Taylor Fritz.

Despite the illness, Zverev has set himself the goal of keeping his career-high ranking at the end of the year.

"For me personally it would be great especially to finish the year as number two in the world," said Zverev, who could be overtaken by Alcaraz, who faces top-ranked Jannik Sinner in the Beijing final on Wednesday.

"Carlos is playing great tennis right now, he's in Beijing making up points, and I know that I have to be at my best to achieve that goal."