Former finalist Marin Cilic has pulled out of Wimbledon after testing positive for COVID-19, the Croatian said on Monday.

The 33-year-old Cilic, who won the U.S. Open in 2014, reached the final of the grasscourt Grand Slam five years ago when he lost to Roger Federer.

"Hey guys, I am sad to share that I tested positive for COVID," he said on his Instagram account, adding that he was "heartbroken" to see his season on grass end due to illness.

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"I have been self-isolating and was hopeful I would be ready but unfortunately I am still feeling unwell and unable to compete at my best."

Cilic, who had been seeded 14th, came to Wimbledon in strong form, having reached the semi-finals at the French Open and also making the last four of the ATP 500 tournament on grass at Queen's this month.

He would be replaced by lucky loser Nuno Borges of Portugal in the men's singles draw, Wimbledon organisers said.