Rafael Nadal says he is in a "difficult" situation as he does not know when he will return from his injury lay-off.
He was initially ruled out for six to eight weeks with a hip injury but has now not played since 18 January.
Nadal confirmed he will miss the Madrid Open, which starts on 25 April, and there is doubt over his participation at the French Open in May.
"The injury still hasn't healed," the 36-year-old Spaniard said.
"I can't work out what I need to compete. I was training, but now a few days ago we decided to change course a bit, do another treatment and see if things improve to try to get to what comes next," he explained in a video posted on his social media channels.