Novak Djokovic blames his recent decline on a premature return from elbow surgery and says he is working hard to rediscover his winning form.
Serbia's former world number one, 30, returned to training two months after his January surgery and fell to successive first-round defeats at Indian Wells and the Miami Open.
"It was my decision [to return] because I missed playing tennis so much," said Djokovic.
"But I was not ready and it backfired."
The 12-time Grand Slam champion is currently ranked 12th in the world and has failed to reach the last eight in any of his five tournaments since making his return.