The Padres' No. 16 prospect fired off six one-hit innings Friday before the Class A Fort Wayne TinCaps dropped a 4-3, 13-inning decision to the South Bend Silver Hawks.
Portillo did not allow a hit until Chris Ellison singled with two outs in the sixth. He struck out four and did not issue a walk, throwing at least six scoreless frames for the fourth time in his last five starts.
TinCaps pitching coach Willie Blair sang Portillo's praises after the 20-year-old right-hander allowed two hits over seven shutout innings on May 3 against West Michigan.
"He's a very intelligent kid, nobody works harder than he does," the former Major Leaguer said. "He's super-competitive and he has a will and a desire to get better. He's a great teammate and competes as hard as anyone I've ever had. He's got a ton of upside, there's really no ceiling. He can be as good as he wants to be."
All of those goose eggs have added up for Portillo, who leads the Midwest League with a 1.48 ERA. He's sixth in the circuit with 50 strikeouts against 24 walks over 54 2/3 innings in 10 starts.
Portillo's raw stuff has always suggested he could put up those kinds of numbers. His results haven't always been in line since he signed with the Padres in 2008, but this appears to be a stretch in which the Venezuelan has figured out a way to make things click.
Six days after that May 3 start, Portillo yielded one hit over seven scoreless frames against South Bend. On May 14, he stifled West Michigan for six shutout frames before Bowling Green touched him up for three runs over 4 1/3 innings on May 19.
Cutting down on his walks appears to have helped. Portillo issued 6.01 walks per nine innings with Fort Wayne last season, when he went 3-11 with a 7.11 ERA in 23 appearances. That figure has dropped to 4.25 this season.
On Friday, No. 18 Padres prospect Jace Peterson doubled twice and drove in a run for the TinCaps.
South Bend walked off with the win, however, when Ender Inciarte scored on a wild pitch by reliever James Needy.