In the final game against Windsor, explain how Tangerine makes one of their goals.

The final game of the season is against Lake Windsor—Paul's old school. The Tangerine team is 9-0-0 for the season, and Lake Windsor is 9-0-1, meaning that this game decides the season. Paul is not initially in the game. He is a sub because he isn't quite good enough to be on the Tangerine team. During the match, Victor gets into an argument with a Lake Windsor player and the player grabs his hair and punches him in the face. There is a scuffle on the field, and Paul is sent in place of the injured Victor.
Because of the scuffle, the Lake Windsor players are not set when the referee blows for the free kick. Paul realizes that this is a great scoring opportunity:

I saw this and screamed, "Go!" I kicked the ball as hard as I ever have, over the heads of the surprised defenders.

Paul kicks the ball to Tino who then passes it to Maya, who puts the ball in the net. It is the first goal of the game, and Paul's involvement is key to the Tangerine team going up 1-0. The goal is unique because Paul plays off the bench for the team—and also because Paul is typically a goalkeeper.
Just as an aside, the second goal by Tangerine was done by Ceasar, a small kid that no one expected to score. His goal keeps Tangerine in the game and allows them to finish with a draw. Both goals are somewhat sensational.