Walker allowed a hit and struck out one batter during a scoreless inning in Sunday's win over San Diego.
Walker made his 2019 debut during Arizona's 162nd and final contest of the season. He threw 11 of 15 pitches for strikes as the team's opener with his fastball sitting around 92-92 mph. The 27-year-old should have a spot in the Diamondbacks' rotation to start next season after he successfully returned from Tommy John surgery.