Q: What’s your opinion about Novak Djokovic’s dominance since he started a gluten-free diet last year? Djokovic won three of the four Grand Slams in 2011 and was on a 43-0 win streak until Roger Federer beat him at the French Open. His win streak ties him with Bjorn Borg for third-best in the Open Era. Only Guillermo Vilas (46-0) and Ivan Lendl (44-0) are ahead of him and Borg.

A: Well, I don’t know anything about gluten-free diets, so I won’t comment on that. But Djokovic is a very solid player in every department and moves with the best. He’s proven this year that he was playing better than the rest, as shown by multiple wins over Nadal and Federer. He has improved, no doubt.

He’s tightened up his game to where he doesn’t have the mental lapses. For a while, the players felt he was a little bit weak mentally when the going got tough. Well, somewhere a long the line he got tougher mentally. He doesn’t freak out or do screwy things mentally. He doesn’t make errors.

Federer makes a few bad errors, and Nadal, if he mis-times one, it can go anywhere. But Djokovic hits so simply into the ball that there’s not too much chance he’s going to make an error.

I think he defaulted in Cincinnati because he said his shoulder was bothering him, but the commentators said, "He looks exhausted to us." And Cincinnati is a tough place to play, and it is so humid you just can’t get dry. I used to dump ice over my shoulders and by the time I got back to the baseline I was sweating again. If you’re not in colossal shape, it’s easy to run out of gas in those places.

You know that big bowl on my dining-room table? It’s because I won it three times. So I’ve played it many times. [Editor's note: Trophies used to get retired when a player or doubles team won a particular event three times.]

I thought Djokovic had played an awful lot of tennis before he took two weeks off after Wimbledon. I think he played it smart in laying low and just practicing and training. Then, in Cincinnati, maybe it was the shoulder, maybe the humidity.

Tut Bartzen, the legendary TCU coach whose 16-0 record in Davis Cup play remains unequalled among Americans, lives in Fort Worth. He coached TCU tennis for 25 years, and the varsity courts are named after him. Send your questions for Tut's Take to This e-mail address is being protected from spambots. You need JavaScript enabled to view it .