Richardson missed class multiple times and failed to complete the punishment given to him for missing the class, sources said.
The 6-foot-4, 295-pound Richardson has 70 tackles and four sacks this season. He is 16th on ESPN's Mel Kiper Jr.'s Big Board for the 2013 NFL draft.
Missouri (5-5) needs one more win to become bowl eligible with a trip to Texas A&M (No. 8 BCS, No. 9 AP) looming in its season finale.
Sophomore Lucas Vincent is listed behind Richardson on the depth chart, according to The Maneater.
ESPN.com's SEC reporter Edward Aschoff contributed to this report.