Clarke had his contract purchased from Triple-A Reno on Tuesday.
The Diamondbacks promoted Clarke to their 40-man roster in order to avoid exposing him to the upcoming Rule 5 draft. Across 27 starts for the Aces in 2018, Clarke posted a 4.03 ERA, 1.27 WHIP and 125:44 K:BB across 152 innings. The 25-year-old right-hander could be in the mix for a back-end rotation spot in 2019.