After work, Stephen decided to join his friends in a game of ice hockey at their neighbourhood skating rink. Ice hockey is his favourite game to play so he played as hard as he could. About halfway through the game, Stephen was injured. He was injured because another player accidentally lost control and both Stephen and the other player fell to the ice, hitting their heads so hard that Stephen got a concussion.

When Stephen took legal action against the ice rink, they raised the defence of volenti non fit injuria. Explain this defence and the likelihood of success.