Cousins, who had just led the Mount Vernon High School boys team to the Class AA state title at this time last March, is now a guard for Sooners.
Oklahoma will meet San Diego State at 8:20 p.m. Friday in Philadelphia in a game televised on TBS Cable in New York.
The Sooners (20-11) are the No. 10 seed in the tournament's South Region bracket, while San Diego is favored as the No. 7 seed.
Cousins, a top recruit after leading the Knights to consecutive New York State Public Schools Class AA titles in 2011 and 2012, chose Oklahoma over several colleges, including Connecticut, Virginia Tech and Dayton.
Cousins averaged 15.8 points, 4.4 rebounds and 4.2 assists and was the top player in Section 1 basketball in his senior year at Mount Vernon.
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