LONDON -- Ever since eliminating pizza from his diet, Novak Djokovic has been on a roll.
Djokovic has been boasting all season about how he has more energy on the tennis court since starting a gluten-free diet, cutting out pizza and bread from his daily life. But the top-ranked Serb has been reluctant to discuss his new regimen in any detail, preferring to let his game do the talking.
The man with the answers is Igor Cetojevic, a Serbian doctor and nutritionist who began working with Djokovic at the end of last year.
"I checked him to see what is going on, gave some advice and therapy," Cetojevic told the Associated Press in a telephone interview. "He started to follow them. He started to sleep properly for the first time in his life."
It actually seems as if it was as easy as that.
Djokovic had won only one Grand Slam title heading into 2011. He now has four after winning the Australian Open, Wimbledon and the U.S. Open, while compiling an amazing 64-3 record this year - with two of those losses coming from injury retirements, including in a Davis Cup match to Juan Martin Del Potro of Argentina last Sunday.
For the past couple of years, Djokovic had been firmly entrenched as the No. 3 player in the world behind Roger Federer and Rafael Nadal. Although he was consistently going deep into the majors, Djokovic's lone big title came at the 2008 Australian Open. Otherwise, he was losing early or even pulling out of matches because he wasn't in good enough shape.
When things started to change, Djokovic hushed up, declining to talk about his new training routine.
"I can't talk about it," Djokovic said at the French Open, "because it's private."
Last month, about two weeks before the start of the U.S. Open, Djokovic again demurred when asked about the diet.
"I cannot tell you everything," said Djokovic, who grew up at his parents' pizza parlor on Mt. Kopaonik in southern Serbia. "There are things that I keep for myself."
But the science behind the decision to essentially cut wheat, barley and rye out of Djokovic's diet isn't all that secret.
Cetojevic said he used a SCIO bio-feedback machine - basically attaching some wires to a person and connecting them to a computer - to study the effects that food has on Djokovic's body. He saw that the gluten was "through the roof," and knew he needed to do something about it.
"We can see most reactions in the body so we can eliminate the bad guys and put good guys in," Cetojevic explained, keeping it as simple as can be.
Cetojevic said the details behind the program can be complicated and he isn't surprised when Djokovic evades questions about the diet.
"He's not a medical doctor," said Cetojevic, adding that even he found it difficult to explain to people what was going on. "He cannot talk about that."
The idea of working with Djokovic came about two years ago, long before Cetojevic had ever met the tennis star. And it started because of his wife, a holistic therapist from the United States.
"I saw Nole playing some match against (Jo-Wilfried) Tsonga in Australia," Cetojevic said. "My wife told me, 'This guy has some allergy.' I said, 'I don't think so. Something else is there.'
"She told me, 'Help him. He's your countryman,"' Cetojevic said with a laugh.
Cetojevic made some calls to people who knew Djokovic and left the message that he might be able to help.
"Time passed, and one day they called me," said Cetojevic, who flew to Split, Croatia, to meet Djokovic for the first time as he played in the Davis Cup quarterfinals against Croatia in July 2010.
It was there that the lessons started, and they involved more than just nutrition.
"I started teaching Nole simple things, like avoid talking on the telephone and eating because you're ignoring your food," said Cetojevic, who also studied traditional Chinese medicine and magnetotherapy. "He started responding very well. Started to kind of eat well, not have weak stomach, vomiting after meals.
"Slowly, slowly he started to build up. I started to observe how he behaves."
The new ideas, including blessing his food before eating in order to have an "emotional, spiritual connection with food," were not completely accepted by some in Djokovic's camp, Cetojevic said, especially after the player started losing weight. But once the results started coming and the weight came back, Cetojevic was hired full time.
"In Chinese medicine, confidence is in the stomach," Cetojevic said.
Even Federer, a 16-time Grand Slam champion and former No. 1, said he doesn't really understand what it is about the gluten-free diet that has made Djokovic so tough to beat.
"I don't even know what that all means," Federer said last month at the U.S. Open. "I eat healthy, and I think that's what people should do, too, if they have the options."
But believing in it, and putting it into effect, is really what matters. And Djokovic has done just that.
Cetojevic sat in the players' box at Rod Laver Arena as Djokovic beat Andy Murray to win his second Grand Slam title at the Australian Open.
Djokovic then ran his winning streak to 43 straight matches before losing to Federer in the French Open semifinals. A few weeks later, Djokovic beat defending champion Nadal to win his first Wimbledon title.
It was Djokovic's desire to win Wimbledon that initially endeared him to Cetojevic.
"When he was a very small boy, he played at home with this little empty pot and on a little chair he stepped on it and said, 'Novak Djokovic, Wimbledon champion.' He was already visualizing what he wants to be," Cetojevic said. "That pure will to succeed touched me."
And after that win, right after Djokovic pulled a few blades of grass from the manicured lawn at the All England Club to physically taste his victory, Cetojevic knew his job was complete.
"I stopped after Wimbledon because that was our goal," said Cetojevic, who returned to his practice in Cyprus. "We had our target."