Jamaal Williams

BYU running back Jamaal Williams plead guilty to being a RESPONSIBLE college kid ... and admitted he had been drinking when he got into a car with a 100% sober driver in Utah back in February. The problem for Williams -- a rising star who's expected to start next year -- is that he's 18 and it's…

BYU running back Jamaal Williams was arrested for underage drinking in Utah recently ... despite the fact he was in a car, on his way home, with a sober designated driver behind the wheel. TMZ Sports has learned ... the 18-year-old sophomore (a rising star who's expected to start next year) was a…