Gaddis was optioned to Triple-A Columbus on Saturday.
Gaddis' contract was selected ahead of his big-league debut Friday against the Astros, but the day didn't go nearly as well as he would have hoped. He lasted just 3.1 innings and left after giving up eight runs. He'll return to the minors for now but could get another opportunity next time the Guardians need a spot starter. Reliever Jake Jewell had his contract selected to take Gaddis' place on the roster.