The Croatian world number 12 eased to a straight sets win over qualifier Evgeny Donskoy in the first round on Monday but his back problem has been an issue recently, having also forced him to withdraw prior to this year's Wimbledon.

The 22-year-old has struggled with his game recently, falling in the second round of the Rogers Cup in Montreal and the first round of the Cincinnati Masters earlier this month.

"I am really sad because I had to withdraw from the tournament," he wrote on Twitter.

"The last couple of months were really tough because of the injury I had. For an athlete, the worst thing that can happen is an injury in the middle of the competition," he said.

"It is never easy to withdraw but at this moment, my body is telling me to stop and assess the situation. So as hard as this decision is, I think it is smart in the long term.

"I am looking forward to playing the US Open next year. Thanks everyone for the amazing support I got here, you make me feel like home," said Coric, who reached the fourth round of the tournament last year.

Bulgarian Dimitrov will get a walk over to the third round where he will face either Pablo Cuevas or Kamil Majchrzak, who hoped to play their second-round match on Wednesday despite rainy weather at the Billie Jean King National Tennis Center.