Gael Monfils has withdrawn from the Miami Open with an ongoing Achilles injury.

The World No. 18 Frenchman has begun the year with a 15-3 record but was forced to withdraw ahead of his Indian Wells quarter-final with Dominic Thiem last week after his left Achilles flared.

"It's not that easy because I was playing well and felt very good in Indian Wells," Monfils said after withdrawing from his scheduled match with Dutchman Robin Haase in Miami. "With treatment it's getting better but it's only been a week and it's not back to 100 percent. I'm confident that it will be good very soon, but I'm not willing to take a risk at the moment. It's definitely a goal to be back for Monte-Carlo."

Monfils is currently sixth in the ATP Race To London, putting himself in early contention to qualify for the elite eight-man Nitto ATP Finals in November.

South African lucky loser Lloyd Harris will fill Monfils' place in the draw