The Arizona Diamondbacks selected Duplantier in the third round of the 2016 Major League Baseball draft. He made his professional debut with the Hillsboro Hops in June 2016, and pitched one inning there, striking out the side. He started 2017 with the Kane County Cougars and was later promoted to the Visalia Rawhide, posting a combined 12–3 record with a 1.39 ERA in 25 games, including 24 starts between both teams. He played in the 2017 All-Star Futures Game. MLB Pipeline named him their Pipeline Pitcher of the Year.
