In Djokovic Rules and Djokovic Still Rules, I've already described how well I think Djokovic is playing this year. Many media pages, like the Wall Street Journal article below, are now devoted to the gluten-free diet he adopted last year - before the streak.

The Diet That Shook Up Tennis?

How did Novak Djokovic conquer the tennis world?

Maybe the answer is as simple as this: Since last year, he's swearing off pasta, pizza, beer, French bread, Corn Flakes, pretzels, empanadas, Mallomars and Twizzlers—anything with gluten.

Hmmm, I love pasta ... pizza ... french bread ... and I've never won a major.

Last year, Djokovic's nutritionist discovered that Djokovic is allergic to the protein, which is found in common flours. Djokovic banished it from his diet and lost a few pounds. He says he now feels much better on court.

A gluten-free diet can have implications far beyond the physical, especially in tennis, which taxes the mind like few other sports. The season is 11 months long, matches are grueling and can last for hours, and the slightest dip in a player's confidence can derail months of hard work. There's never anyone else to blame for a match gone awry.

"It's mostly mental energy you're talking about, not energy supplied to muscle tissues," said David Levitsky, a professor of nutrition and psychology at Cornell University, when asked about the effects of giving up gluten if one has an allergy. (An allergy differs from celiac disease, whose sufferers, Levitsky said, can incur far-reaching health effects from eating gluten, including the inability to absorb nutrients.)

Levitsky said a gluten-free diet might have benefits for those with mild allergies, or even no allergy at all. "The other part of the story is, if you believe in a cause of your disorder, it becomes the cause," he said. "We see this in many different studies. If you believe it, you change your behavior in the direction of being cured."

And in case you thought I was exaggerating about his performance:

But no one would have predicted what has transpired since January. Djokovic's season has gone from good to great to outrageously, impossibly, unrealistically phenomenal. In an age when even small sports achievements can get enormous hype, there's really no superlative to describe what the soon-to-be 24-year-old has done this year.

There's some serious diet plan money to be made here.