Bukauskas was optioned to Triple-A Reno on Wednesday.
Bukauskas earned his second win of the season Tuesday by striking out two in a perfect inning against the Pirates, but he'll now head back to the minors after strong performances in each of his last two innings. Although the right-hander has a 7.98 ERA and 1.84 WHIP in 14.2 innings across 18 appearances in the big leagues this year, he could rejoin Arizona's bullpen at some point if he performs well at Triple-A Reno.