Serious football chops from both players.
Rafa Nadal was a football player before he turned to tennis and his uncle Miguel Ángel Nadal nicknamed The Beast played for both Real Mallorca and Barca. He also represented Spain earning 62 caps. So there is a lineage of football behind tennis's numero uno.
From what one sees, Nadal would have been a ball hog - an Arjen Robben. Whereas Novak Djokovic would have been a ball distributor like Dejan Stankovic.