All you need to do is go back and watch Owen Grant play for Team Canada this summer against University of Virginia and the best players on Team USA (LaxSportsNetwork.com still has these games archived). He is a caused turnover machine. He always takes on the opponents top attackman and basically shuts them down. Grant is a one-man clear and instant fast break on any loose ball around the crease as well.
There are a ton of great close defensemen so it is really tough to rate them in order from 1-10. But I believe you will see Grant in the top four defensive picks in the PLL late this spring. Will Bowen, Brett Makar and Gibson Smith have better name recognition, but having watched all of them play, he is on that same level or better.