Buchter was returned to Triple-A Reno on Friday, Steve Gilbert of MLB.com reports.
Buchter spent the last week in the Diamondbacks' bullpen while the team dealt with a COVID-19 outbreak, and he allowed three runs on five hits and no walks while striking out three in 1.2 innings across two appearances. The southpaw will head back to the minors after Joe Mantiply was reinstated from the COVID-19 injured list.