This paper introduces an original approach to automatically select a Region of Interest in an image that represents a 3D scene. We assume that the Region of Interest background is significant enough to be characterized by its color and its spatial coherence. We use these two features to provide such a selection that is the first step of a 2D to 3D registration process for analyzing video captured sport scenes. The whole project includes the 3D reconstruction of the scene (players, referees, ball) and its animation as a support for cognitive studies and strategy analysis.