Herrera compiled an 18-7 record and 3.27 ERA pitching professionally in Cuba. He defected after being left off the nation's Olympic roster in 2004, wound up in the Dominican Republic and impressed the Bucs during a tryout in August.
The Pirates signed the pitcher, who turns 26 on April 28, to a three-year contract worth $1.92 million in December.
Herrera was pumped up for his first start.
"I'm excited, and I feel great, 100 percent," Herrera said, with the translating help of Curve catcher Milver Reyes. "This is the next level, a big level for me and I'm so excited to be a professional now."
Altoona pitching coach Ray Searage liked what he saw from Herrera.
"He did an excellent job," Searage said. "I didn't think he'd have that good of a feel for his curveball today, and his changeup was working outstanding with the command.
"All his pitches were down in the zone, had good command, very good poise on the mound. Very positive outing for him and something to build on."