Camilo Villegas was a young superstar in the making. He has recently lost his way. Mainly because his swing is very athletic, needs a lot of strength but is in not fundamentally sound.
I believe in reducing unnecessary motion and building a simple repeatable motion. He has way too much extra movement. If his timing is right he can shoot low numbers, but unfortunately he can also shoot himself off the main tour.
He is using a great drill in the video above. If you find your ball starts is curving too much to the left or right of your target then try this drill. It helps you develop a straighter path through the ball.
The ball flight laws tell us that the primary influence on a golf shots initial direction is the club face. The curve of the shot generally comes from the club path in relation to the club face. Therefore if a player has a swing path that cuts too much across the target line then they will likely over curve the golf ball, making it harder to control.
Camilo Villegas is practising his swing path so that he will ahve better control over his ball flight.