Third-seeded Milos Raonic of Canada withdrew from the Miami Open on Sunday with a hamstring injury.
Raonic had been scheduled to play American qualifier Jared Donaldson in a third-round match.
“It's related to the previous injury I sustained almost four weeks ago... in Delray Beach,” he told reporters.
"It's the same muscle in the hamstring up high. It got progressively worse after my first round. It seemed like it was not possible for me to compete today without putting myself at significant risk."
Raonic said he would not return until he felt 100 percent fit again.
"That could be in two weeks; that could be a little bit longer."
(Reporting by Gene Cherry in Salvo, North Carolina; Editing by Clare Fallon)