Bargnani is playing great, but I don't really understand this statistic. It obviously is not the same as points per 100 possessions (ie, defensive rating) because if I look on basketball-reference.com, Bargnani has a DRating of 105.
Doing a quick search of all players who played a minimum of 10 games, Bargnani is ranked 197th:
http://www.basketball-reference.com/...asc=Y&offset=0
105 is pretty good, but that doesn't make him a great defender. I'd think anything below 100 is the mark of a great defender. 105 is about an average defender. The one thing that I like about his defense this year is that he doesn't appear to be a liability on that end like he has been showing in previous years.