Quick and easy if you have 2 controllers.
Go to Exhibition, 1v1, No Bots, and change the weight of the ball to Heavy.
Enter the game and with the dummy controller, just drive forward and knock the ball towards the goal. Your main controllers' car will already be in the way, and when the ball hits it, it will count as a save.
Pause, Restart, and repeat 19 times for the achievement.