Rafael Nadal, challenging Juan Martin del Potro for the Indian Wells title on Sunday, won't play the Miami Masters that starts later in the week, organizers said.
"The Sony Open has been notified by the ATP that Rafael Nadal has officially withdrawn for the event," a statement from organizers said.
Tournament director Adam Barrett said he didn't know the reason, but Nadal's run to the final in Indian Wells was his fourth in four tournaments since he returned in February from a seven-month injury absence.
Skipping Miami would allow him to rest his troublesome left knee and begin his preparations for the clay court season.
"We are disappointed to hear the news that Rafael Nadal will not be competing in Miami this year, especially given his strong results since his return to the Tour," Barrett said.
"We wish him well and hope to see him back in Miami next year."