Diaz attended Acalanes High School in California. He batted .406 in his senior season, collecting 10 RBI. He was ranked the 12th overall prospect in California, and the 6th best shortstop in the state by Perfect Game, and decided to join Vanderbilt following his high school career.
As a freshman with Vandy, Diaz slashed .213/.353/.293 (average, on base
%, slugging). He played in 59 games and hit 9 doubles and 2 home runs, driving in 20 RBI. He showed his patience at the plate, drawing nearly as many walks as hits on the year.
Last season as a sophomore, Diaz slashed .263/.376/.415, driving in 57 RBI on 7 doubles and 9 home runs in 62 games played. He stepped into a full time starting role in this season.
This year is Diaz's junior season. He is expected to take a step forward and improve his draft stock from when he was drafted in the 12th round out of high school. He will need to show more consistency with the bat.