I would view anything that could be thought of as a 'game' or 'sport' under the athletics (wrestling, fencing, kendo, Anbo-jyutsu) mantle and any skill that is used in real combat situations under the relevant combat skill. Answering the OP though, yes you could do that I suppose but it would not be as good as someone with the relevant 'real' skill.
A skilled person in, say fencing would not fare well against an equivalently skilled Historical European martial arts (HEMA) specializing in the rapier. One is used to/training to scoring 'hits' for points the other is used to/trained to disable/kill his opponent. The same could be said about a wrestler verses a Judo practitioner (maybe to a lesser degree but the logic is sound). One is a sport the other is a combat skill. Sports tend to introduce too many rules into a thing to render it useless in a real world application. With that being said though, it would be better to be (using the fencing example) to be a trained fencer and go up against a trained rapier user than be untrained and having to face a trained individual.
AKA-Dean
"I will never make excuses for who I am. It is the way I was born. I am a HUNTER. a BONE COLLECTOR."
Wave Man, the term "wave man" is the English translation of 'Ronin' (Japanese word) and literately translates to "wandering person" and in a modern context a WaveMan is one who is socially adrift or a SalaryMan who is between employers.