You will need strong shoulders amd triceps to throw the ball.
Do heavy military presses and close grip bench presses.
I am a big fan of soccer and I also play, Check out the Jillian Micheals 30 day shred workout on youtube. That workout wil surely get you ripped and ready for soccer season. Good luck
Lift some weights. Do bench presses and military presses. Also do tricep dips and arm curls