keep one's eye on the ball

1. To watch the ball at all times in a sport, usually in order to hit it or get it; not stop watching the ball.
Keep your eye on the baseball or you won't be able to hit it.
2.  {informal}
To be watchful and ready; be wide-awake and ready to win or succeed; be smart.
Tom is just starting on the job but if he keeps his eye on the ball, he will be promoted.
Categories: informal verb