'There is a significant risk of increasing the injury and I have no choice.'
Top seed Rafael Nadal pulled out of this week's Mexican Open in Acapulco after aggravating the leg injury that forced him out of the Australian Open last month.
The world number two, who was due to face fellow Spaniard Feliciano Lopez on Wednesday, said he felt a sharp pain during his final training session on Tuesday and decided not to compete on the advice of his medical team.
"Doctors have told me that it is impossible to play, regardless of whether it hurts," said Nadal. "There is a significant risk of increasing the injury and I have no choice.
"I was well prepared to play and I had hopes of doing something important here."
Nadal, who has not competed since retiring against Croatia's Marin Cilic in Melbourne last month, was in Acapulco hoping to close the gap on world number one Roger Federer.
"I still don't know what it is, because we don't know. It seems it's not as bad as what I had at the Australian Open," the 31-year-old added.
"Now my main goal is to find out the extent of the injury."
Kyrgios bemused by lack of action on Gavrilova tantrum
Outspoken Australian Nick Kyrgios has bemoaned a recent outburst by Daria Gavrilova, saying that he would have been "banned for six years" had he behaved in a similar manner to his compatriot.
Gavrilova lost her temper during a match against American Madison Brengle at the Acapulco Open on Monday, the Australian throwing her racket after misfiring on a serve and nearly hitting a ballkid.
The racket then bounced up and slammed into the umpire's chair, yet Gavrilova escaped punishment and went on to win the match 4-6, 6-3, 6-3.
Kyrgios, known for tantrums and controversial moments of his own, tweeted a video of the incident and wrote: "I would be banned for 6 years and been on every paper and news channel for the next month."
American Coco Vandeweghe, who has also found herself in trouble with tennis authorities, appeared to support Kyrgios with a reply to his tweet that included an emoji of a woman shrugging.
"Double standards everywhere," she commented.