In a perfect world a physical d-man does use his physicality to stop the cycle game, enabling his team to get the puck but generally physical d-men aren't that effective. Lidstrom was one of the greatest d-men that ever lived but he wasn't flashy physical, he would angle an opponent towards the boards with the intention of getting the puck and moving it out of his defensive zone or pass it too an open teammate. Brodie isn't bad, he's not really physical but he uses his gifts, the greatest being his brain, to enable him and Rielly to be a reasonable facsimile of a 1st pairing d, why are they effective even tho neither are physical, it's because they can move the puck, retrieve the puck, pass which are the essential talents of d-men. Physicality as a primary talent is a significant ways down on the criteria of most GMs and without a reasonable puck game all d-men are useless.