Walker, who was selected by the D-backs off waivers from the Reds in March, tore up the Pacific Coast League while playing for Triple-A Reno. He led Minor League Baseball with 114 RBIs while smacking 34 doubles and 32 homers.
For his efforts, Walker, ranked No. 27 on the D-backs' Top 30 Prospects list, was named the Pacific Coast League's Most Valuable Player.
Even better for him, his performance earned him a September callup to the D-backs where he went 3-for-12 with a pair of home runs.
Duplantier, the D-backs' No. 2 prospect and MLBPipeline's Pitching Prospect of the Year, was the team's third-round selection in the 2016 Draft.
The 23-year-old former Rice pitcher, was 6-1 with a 1.24 ERA in 13 games (12 starts) for Class A Kane County before earning a promotion to Visalia in the California League.
The jump didn't slow down his results as he went 6-2 with a 1.85 ERA in 12 starts.
Last week the D-backs named Duplantier their Minor League Pitcher of the Year.
Each team's Hitting and Pitching Prospects of the Year were chosen by the MLBPipeline.com staff. To receive consideration, players must have spent at least half the year in the Minors, appeared on the team's Top 30 Prospects list and played the entire year in the organization.
Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.