"I'm really blessed and happy," Guduan said through a translator before the game. "I knew it was going to happen, and it happened today."
Guduan, who has an upper 90s-mph fastball and sharp slider, took the bullpen spot of Jordan Jankowski, who threw 46 pitches in Monday's game and was sent down following his first Major League win. Guduan, 25, was 3-3 with one save and a 5.47 ERA in 20 games at Triple-A Fresno, including a 1.69 ERA in May.
"I'm not sure how he's going to be used yet other than an extra reliever," Astros manager A.J. Hinch said before the game. "I love the arm strength. I think his slider is effective certainly against both sides of hitters. The key for him is going to be in the strike zone. He's going to have to corral his emotions of being up for the first time in the big leagues. In general, when he's a strike thrower he's been effective in Triple-A, and when he's not, it's been a little bit tough for him.
"Exciting arm and someone who gets an opportunity because of the ever-changing rotation we have both in the bullpen and in our rotation. I hope to get him in there and get his feet wet."
The Astros have three starting pitchers -- Dallas Keuchel, Charlie Morton and Joe Musgrove -- go on the disabled list in the past two weeks, though Keuchel has since returned. Long reliever Brad Peacock has been moved to the rotation, which created an opening in the bullpen.
Brian McTaggart has covered the Astros since 2004, and for MLB.com since 2009. Follow @brianmctaggart on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.