The Illini (9-0) couldn't shake the pesky Catamounts until late in the game when Richardson canned two 3-pointers to spark a decisive 12-2 run.
Brandon Paul put in 14 points and Tracy Abrams added 10 as Illinois avoided a potential major upset.
Preston Ross and Brandon Boggs combined for 33 points for Western Carolina (3-6), which was seeking its first-ever win over a nationally ranked opponent.
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