How bad of a defensive player can you be and still not hurt the team?

I’m sure the NBA Analytics guys have probably already answered this. But there is a discussion on BobcatAttack as to whether Bean Willis gives up as many points as he gets. Looking at KenPom, Willis as on offensive rating of 120.0 (points per 100 possessions). There are  no individual defensive rating to help net that out so I decided to look at the defensive rating of the worst team in the country. Longwood allows 113.0 points per 100 possessions. Granted, Willis could be  a worse defender than that of the worst team in the country. Assuming that he would be an average performer on the worst defensive team in the country, you would still be up 7 points per 100 possessions.