Defending champion Juan Martin del Potro has withdrawn from the BNP Paribas Open at Indian Wells with a knee injury.
The world No 4, who defeated Roger Federer in the California tournament's final last year to win his first Masters 1000 title, returned to competition after a four-month absence from a fractured right kneecap at the Delray Beach Open last week.
Del Potro had his knee heavily strapped in Florida and lost in the quarter-finals to American Mackenzie McDonald.
"I am truly disappointed that I will not be able to return... to defend my title," Del Potro said of the Masters 1000 event that starts on March 4.
"It is one of my favourite tournaments, and I have incredible memories from last year, but my doctors have advised me to rest. I hope to be back on court soon."
Del Potro had already pulled out of this week's Mexican Open in Acapulco.
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