Novak Djokovic tells USA Today that his father Srdjan was gravely ill last year.

“He was very close to dying,” said Djokovic, who did not identify what his father was suffering from other than that it involved the sacral bone in his spine.

Djokovic said his father spent two months in a hospital and one more in a rehab center. He is now able to go on a treadmill, but is not at 100 percent health.

“For last six months it was tough time for him and for the whole family,” Djokovic said. “But he managed to push it through with the support of close ones and because he’s also a very mentally very tough person. I think the desire to live and to spend times with the close ones helped him to overcome the illness.”