Clarke was optioned to Triple-A Reno on Thursday, Zach Buchanan of The Athletic reports.
Clarke was never expected to open the season in Arizona's rotation, but the team's decision to send him to the minors to begin the season indicates he'll remain stretched out as starting depth. The righty made 23 appearances (15 starts) with the Diamondbacks in 2019, compiling a 5.31 ERA and 1.37 WHIP across 84.2 innings.