When you put your hands up around your face like that, you cannot punch back, and Lacy needed to punch while Calzaghe was punching. Instead, he tried to wait it out. But, as mentioned above, Calzaghe would throw a bunch of punches, then step over and throw a bunch more. Because he didn't know how to fight, because he never bothered to learn, Lacy didn't know what to do besides cover up and hope the other guy would get tired of hitting him.