Though he did allow three runs in his most recent appearance on Wednesday, Schugel had been charged with just two runs over his prior 11 outings covering 12 2/3 innings.
"Not about performance at all," manager Clint Hurdle said of Schugel's demotion. "It's about having [Minor League options available], and [that there are] three men in the bullpen now who are already length possibilities. ... [Juan] Nicasio, [Jeff] Locke, [Jonathon] Niese all have length, so with two days off [next week], a combination of things with the schedule.
"It's not about performance at all; he's been a valuable guy out there, and I believe he will be a valuable guy again before the season's over."
Schugel, who had five games of Major League experience before this season (all with the D-backs in 2015), has a 3.94 ERA with 40 hits allowed, 13 walks and 41 strikeouts in 48 innings.
The son of a longtime big league scout, Schugel understands as well as anybody that roster moves are part of the game. He took the news in stride.
"I think I did enough to stay, but it's just one of those things," he said. "It's baseball. And hopefully it's short-lived and I'll be back."
Glasnow was recalled to make his second Major League start Saturday. The Pirates had been carrying an extra man in their bullpen because of the All-Star break and a stretch of a spate of off-days.
Chris Adamski is a contributor to MLB.com and covered the Pirates on Saturday.