Juan Martin del Potro said that he was battling illness after he suffered a shock defeat in the China Open final on Sunday, losing 6-4, 6-4 to unseeded Nikoloz Basilashvili of Georgia.

In the women’s final, world number two Caroline Wozniacki defeated Latvia’s Anastasija Sevastova 6-3, 6-3 for her 30th WTA singles title.

Argentine top seed Del Potro was clearly far from his best and has been fighting flu or a cold for several days in the Chinese capital.

The world number four said that he did his best in difficult circumstances.

“I did everything that I can to be better for the final, it wasn’t enough time to feel 100 percent,” the 30-year-old said.

“As you can see, my game today wasn’t as good as it was in the last matches in the tournament. I had some problem the last three days and it affected a little bit my game.”

Del Potro, who reached last month’s US Open final and is enjoying one of the best seasons of his injury-interrupted career, is now in a race to be better for this week’s Shanghai Masters.

“I wasn’t able to play with that fire that I have in all my matches,” Del Potro added, saying however that 34th-ranked Basilashvili “played unbelievable”.

It is only the second title of 26-year-old Basilashvili’s career, having won his maiden ATP title in Hamburg in July.