the skills of the players involved. If your team has better players, you win. If not, you lose.
Between games, you can train your player. There are several different kinds of workouts. For one, there's a typical practice, where you play a kind of board game where you roll the dice to see which box you land on. There's also intensive training, where you play other skill games.
A fun detail is that you can customize your player. When you create your player, you can choose the nose, eye color, hair color, and so on. As you continue playing, you can customize more and more aspects.
Pocket Footballer is a soccer game that doesn't actually let you play any soccer. However, it's still a very entertaining game with some good Nintendo-style graphics.