Ruiz was the 4th round selection of the Houston Astros in 2012 out of high school in California. In his draft season, he played for the Astros Arizona Rookie League team and their Greeneville team in the Appalachian League. Combined between the levels, he hit .252/.336/.400 in 152 plate appearances with a 10.5% walk rate and 21.1% strikeout rate.
In 2013, the Astros sent him to their full season A-ball team in Quad Cities in the Midwest League. Over 472 plate appearances, he hit .260/.335/.430 with 12 home runs and 12 stolen bases along with a 10.6% walk rate and 19.