Novak Djokovic Works Out In Speedo, Check Out My Djunk!

Less is more when it comes to training gear for Novak Djokovic ... 'cause dude went for a run on the beach in Spain wearing sneakers and a Speedo.

Djok was hangin' out in Marbella when he decided to get in a workout while taking in some sun -- so, he hit one of the public beach gym places and started grindin'!

... in his budgy smuggler.

He ran. He did pull-ups. Leg press. All while leaving little to the imagination.

Look, he's from Europe (Serbia) and was in Europe (Spain) ... and everyone knows they love their man panties across the pond.

Plus, Novak's got a killer bod.

Of course, Novak is now in New York for the U.S. Open ... so, it's all business from here on out.