Rafael Nadal -- Screw Tennis ... I'M GONNA DOMINATE POKER

Rafael Nadal is taking some time away from the court ... and heading to a casino in Prague ... where the tennis god will compete in his very first live poker tournament.

The 27-year-old tennis champ has signed up for a live charity poker tournament in the Czech Republic on December 12 as part of the European Poker Tour.

Rafa has been training with a poker coach and is taking the "sport" very seriously ... saying, "It's no secret that I love the competition and that's what I like about poker."

He added, "It's a game of skill that requires mental strength and the ability to out-think your opponents and in that way there are similarities to tennis. I have been playing poker online for almost 18 months and now I'm looking forward to the challenge of playing my first live tournament.."