Linebacker Victor Butler was also put on the PUP list with a torn ACL, likely to hold him out for the entire season. Robinson is trying to return from a knee injury while Harper's injury is undisclosed.
Harper has been one of the Saints' mainstays on defense throughout the Sean Payton years, being one of the key players who was part of New Orleans Super Bowl run a few years ago. At 30, Harper set a career-high in tackles last season with 115. In 2011, Harper showcased his versatility by amassing 7.5 sacks from the safety spot.
Robinson is a former first-round pick from the 2010 class. Last year, Robinson started all 16 games for the Saints and made three interceptions to accompany 64 tackles.
Both Harper and Robinson will be getting used to their third defensive coordinator in as many years when they return, with the hiring of Rob Ryan.