Prosecutors say the incident happened when the Sacramento area Christian Brothers High School team was in Orange County for a championship game in Irvine on December 5, 2009.
Prosecutors claim Nguyen went to the 17-year-old female player's hotel room under the pretense of giving her an athletic massage. He is accused of moving her clothes to expose her breasts and vagina during that massage. He is not accused of touching her inappropriately.
If he is convicted Nguyen faces up to a year in jail.
