If one good thing came out of the six months of tournaments that Rafael Nadal missed because of chronic left knee problems, it was that the tennis superstar picked up a new hobby.

During those difficult months at the end of 2012, Nadal was introduced to poker. He's come to love the sport and spends hours upon hours playing online. On Dec. 12 he'll be participating in his first live tournament, and he's got some good company.

Soccer stars Ronaldo and Andriy Shevchenko will join Nadal at the charity tournament in Prague, along with several other European athletes and poker pros.

"Ronaldo has always been a hero of mine and I'm looking forward to taking him on at the poker table," Nadal said in a statement. "There are many similarities between sport and poker strategy, so it will be good to see how he translates his game from the football field to the poker felt."

The charity tournament's pool is 100,000 euros (about $135,000).

Nadal has risen to the top ranking in men's tennis after a stellar fall season that included a U.S. Open title. The 27-year-old will likely be a favorite at next month's Australian Open, the only Grand Slam tournament that he hasn't won multiple times.

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