World No. 2 Rafael Nadal said Sunday that back pain could keep him from pursuing his 21st Grand Slam title at the Australian Open, which begins Monday.
He didn't play this week for Spain in the ATP Cup and has appeared in just one exhibition match since the ATP Finals in London in November.
"Not great obviously," he said of the timing of the back injury. "It's true that for the last 15 days I have been suffering.
"In the beginning, the muscle was just a little bit tired but I feel a little bit more stiff than usual."
Nadal, 34, has continued to mix practice with medical treatment this week in an effort to be fit to play in Melbourne. He is scheduled to meet Laslo Djere of Serbia in his opening-round match on Tuesday.
While categorizing the injury as "not serious," he said it's tough to play through it.
"The muscle is still tight, so it is difficult to play with freedom of movement," he said.
"We are doing everything. My physio is here, the doctors here, everybody is helping me in all possible ways. I hope to be ready, that's all. I know sometimes things change quick."
The Australian Open is Nadal's first opportunity to become the all-time leader in Grand Slam titles among men. With his win at the French Open last fall, he tied Roger Federer at the top of the list with 20.
Federer, who is coming off knee surgery, will not play at the Australian Open, instead choosing the make his season debut next month at Doha.
Nadal has one victory in Melbourne, coming in 2009 when he defeated Federer in five sets. He has won the French Open 13 times, the U.S. Open four times and Wimbledon twice.
--Field Level Media