Penny, 36, is a two-time All-Star, and he was part of the Marlins' rotation on the 2003 World Series championship team.
Penny's return on Saturday night wasn't picture perfect. He labored with command, walking four and getting into many deep counts over five innings. But he minimized damage, showed composure while pitching at his own tempo.
Manager Mike Redmond hopes some of his young starters were paying attention.
"For young guys, sometimes when it starts to snowball, it leads to the big inning," Redmond said. "We've seen that a few times this year. With veteran guys, they continue to make pitches, knowing they're only one pitch away from getting out of any situation. We saw Brad do that."
Penny gave up two runs (one earned) and picked up the win in Miami's 4-3 victory over the Reds.
In a career that started with the Marlins in 2000, Penny has logged 1,904 big league innings, which is more than the total of the team's other five starters combined. Currently, Henderson Alvarez is on the disabled list.
Alvarez (491 1/3 career innings), Nathan Eovaldi (411 1/3), Tom Koehler (137 1/3), Brad Hand (151 1/3) and Jarred Cosart (181 2/3) have combined for 1,531 1/3 innings.
"Hopefully, I can show them how you go about being a professional," Penny said. "There is a lot of talent on this team. I'm lucky to get another opportunity to pitch at this level."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter