Butto was optioned to minor-league camp Monday, Tim Healey of Newsday reports.
Butto was added to the 40-man roster in November but isn't quite knocking on the door of the active roster. He's yet to reach Triple-A and only made eight Double-A starts, though those went quite well, as he struck out 29.9 percent of opposing batters and walked just 5.4 percent en route to a 3.12 ERA.