Wojtek Fibak, the former Polish star who advised Djokovic at last year’s United States Open, said he used that for fuel again when Djokovic was upset after his semifinal with Stan Wawrinka was scheduled first during the day after he had played primarily night matches.

Fibak said Djokovic had “the worst warm-up” and was in “a horrible mood” so he tried his best to get him back to the essential. “I said, ‘Remember your parents, remember your father had to sell his car for you to play tennis,’ ” Fibak said. “I kept bringing it up, and Novak’s eyes were big, and I said: ‘Do you know why they did it? So you could play the U.S. Open, and now you are in the semis of the U.S. Open and you don’t want to fight and you’re not happy just because of the time? I said do it for your father, your mother, for Serbia.’ And Novak all fired up now goes, ‘Serbia! Serbia!’ ”

He went on to beat Wawrinka in five sets before losing to Nadal in the final.

Now, as he returns to the tournament he wants to win more than any other, Serbia is again at the forefront of his thoughts. He has been seriously involved in raising money and awareness for relief efforts after this month’s floods in southeastern Europe, primarily in Serbia and Bosnia and Herzegovina, that killed dozens and forced hundreds of thousands from their homes.

Djokovic has donated his prize money — listed at 549,000 euros, or $750,000 — from winning the Masters 1000 event in Rome.

“I’ve seen the images and followed the news every single day, and it was something I’ve done because I felt like that was the right thing, and that’s it,” Djokovic said. “The second thing I thought about was that it was going to attract more of the donors from the international world to see that the situation is as serious as the prize money I donated. We’re talking about billions of dollars needed.”