Portillo, who is on the 40-man roster, will be at his first big league camp, alongside pitchers with considerably more experience.
"I'm so excited," Portillo said. "I just want to get experience from the pitching coaches, the older guys … like Clayton Richard. I want to learn more about how to pitch, what count to throw certain pitches. For me, I can't wait for the first day of Spring Training."
Portillo is rated as the sixth-best prospect in the Padres' Minor League system.
Last season, Portillo started at Class A Fort Wayne and was 6-6 with a 1.87 ERA in 18 starts. The Padres then decided to challenge him, having him skip over Class A Advanced Lake Elsinore for Double-A San Antonio, and he was among the youngest players in the league.
Portillo was 2-5 with a 7.20 ERA in eight starts for San Antonio. But he said that time proved valuable for him, as he knows a little better what to expect there this season.
"That helped me a lot," he said. "I'll start in Double-A again this year and I feel I know the league, all the different stadiums. Hopefully I'll have a good year in Double-A and eventually get here [San Diego]."
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.