Novak Djokovic, for one, has credited breathing exercises with helping him ... Through the day, take a few deep breaths, diaphragmatic breaths; this will make it feel more natural when you ...

BELGRADE, Serbia (AP)—Top-seeded and defending champion Novak Djokovic retired with breathing problems during his quarterfinal match against Filip Krajinovic at the Serbian Open on Friday.

That’s why the moment it ended, Djokovic let out a belated roar towards his court-side box, where Andy Murray paused for a deep breath. Djokovic went up and singled out coach Murray for a hug.

This match, delayed several hours due to rain, featured the illustrious six-time champion Novak Djokovic duking it out against the promising 19-year-old Czech sensation, Mensik. With tennis ...