Marin Cilic says he is not able to play Wimbledon because he tested positive for COVID-19.

The 2014 U.S. Open champion and 2017 Wimbledon runner-up wrote on Instagram on Monday that he has been self-isolating and was hoping he would get better in time for the tournament.

But he added that he is still feeling unwell.

Cilic will be replaced in the draw by 123rd-ranked Nuno Borges of Portugal.

Borges lost during qualifying for Wimbledon. Now he will face Mackenzie McDonald of the United States in the first round of the main draw on Tuesday.

Cilic was coming off a semifinal run at the French Open earlier this month. That made him the fifth active man to complete a full set of semifinal appearances at all four major tournaments, joining Rafael Nadal, Novak Djokovic, Roger Federer and Andy Murray.