Throwing the ball properly is important no matter what position you play. If you don’t throw well you are severely limited on what positions you can effectively play defensively. Many people have told me that backside arm action is natural and can’t be taught. I beg to differ. I was taught to throw as a child using a tennis racquet as a teaching aid, and I have successfully used it with young players to teach them the way to properly internally rotate the elbow - which is the most common problem I see with bad arm action. The proper arm action for throwing is the same as serving a tennis ball.