OK, so in last night's game, Wallace caught a ball, took three steps, got hammered, and lost the ball which went out of bounds. Called catch, challenged and upheld. If the defender would have hit him from behind, knocked him to the ground, and he lost the ball, would that fall under the Calvin Johnson/Arian Foster rule and have been ruled an incompletion? I'm not understanding the difference between all the rulings. Anyone know what the difference is?