The Illini (11-0) were coming of a win at Gonzaga on Saturday that helped move them into the top 10, but were sluggish against the Spartans. Illinois was shooting 46 percent from the field coming in but shot just 35 percent on the night.
Rashid Gaston scored 12 points and Pendarvis Williams added 11 for Norfolk State (6-6), which led for much of the first half.
Richardson left late in the first half with a badly bruised shoulder but returned. His layup with just under two minutes remaining put the Illini up 56-51 and they went on to get the win.