This is the final mission that involves playing a game with one of the Victory Dogs. When you enter Rune Villiage and go near the entrance to Rune Canyon, McCoy will appear and challenge you to a game of soccer, which is really just the dogs pushing the ball around, since it is bigger than them.
The first dog to score 3 points wins.
If you win, McCoy will admit that he underestimated you and give you his badge. However, if you lose, he will laugh at you and call you slow. This is a mandatory mission, meaning you will have to defeat him at some point or another. After beating McCoy, Petasi will say he thinks they have beaten all of the Victory Gang dogs.