Richards, a senior, was arrested for operating while intoxicated and minor consumption of alcohol last December. He was sentenced to a year of unsupervised probation in February.
A two-year starter, Richards was third on the Boilermakers with 64 tackles last season, adding an interception and a forced fumble.
Purdue opens the season against Western Michigan on Aug. 30 and Central Michigan on Sept. 6. Richards will be back for the Boilermakers' game against Notre Dame at Lucas Oil Stadium in Indianapolis on Sept. 13.
- Ben Estes