Porcello allowed one run on one hit and struck out three over eight innings as Toledo defeated Louisville, 6-1, on Thursday.
The Tigers' first-round pick in 2007 was sent down to Toledo on Sunday after going 4-7 with a 6.14 ERA in 13 starts for Detroit. Thursday marked the first Triple-A start of the 21-year-old's career, as he reached the Majors in 2009 after a year with Class A Advanced Lakeland.
Porcello (1-0) thinks the Triple-A experience will help in the long run.
"I think it's good for me to come down here and work on a couple of things and get some confidence," he said.
Porcello, who was drafted out of high school, felt at ease with his breaking pitches Thursday.
"I had a pretty good sinker tonight and a good slider," he said. "It was a pretty effective mix of pitches.
"I'm just trying to work on my slider and try to shorten it up a bit and throw it consistently for strikes down in the zone. I felt comfortable with it tonight. That's pretty much what they wanted me to come down here and work on. That and to keep my sinker down in the zone."
The right-hander allowed a one-out double to Juan Francisco in the fifth inning. Francisco later scored when shortstop Brent Dlugach committed a throwing error on Ryan Hanigan's grounder. Porcello, who walked one and also hit a batter, credited Francisco for putting a good swing on the ball.
"It wasn't really a bad pitch," he said. "He battled off a couple of fastballs, and he got one up in the zone and got a pretty good piece of wood on it."
Porcello exited after 85 pitches, but said he felt strong enough to have pitched the ninth.
Wilkin Ramirez slugged his third home run since being promoted to the Mud Hens (41-33) on June 8. Ramirez finished with three RBIs, while Jeff Larish singled and drove in two. Will Rhymes had two hits and stole his 15th base.
Casey Fien completed the one-hitter by striking out one in a perfect ninth.