For younger basketball players you really have to stress dribbling with your eyes up, or they are going to continue to dribble with them down, and it will set them back as they get older, and begin to play against better competition. This tennis ball toss between the legs basketball dribbling drill will not only help work on the players ball handling, but it will also help the player to learn to dribble with their eyes up. It will also develop their hand eye coordination as well.
Whether the player is primary ball handler or not, this is a good basketball drill to do because you are developing the players hands. Also, learning to dribble the basketball and not having to focus on it, is good practice for when you are trying to read the defense and run the offense as a ball handler. You will be able to handle the basketball without constantly having to look down at the ball.