Witherspoon went 11-of-11 from the floor, including 3-for-3 from 3-point range.
Joe Jackson added 20 points with seven assists for the Tigers (1-0), who led by as many as 18 at 70-52 with 12:18 left in the game. Adonis Thomas added 12 points off the bench for Memphis.
The Bruins (0-2) were led by J.J. Mann with 18 points and Ian Clark with 16.
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