The 36-year-old pitcher has played for the Marlins, Dodgers, Red Sox, Giants, Cardinals and Tigers. He signed a minor league deal in June.
Penny went 48-42 with a 4.04 ERA with the Marlins from 2000-04, when Mike Redmond -- the Marlins manager -- was his catcher. He won 14 games on the Marlins team that won the World Series in 2003. His last start for the Marlins was July 28, 2004.
Penny hasn't played in the majors since 2012, when he made 22 relief appearances for the Giants. It was the first time in his career that he didn't make at least one start during a season. His last start in the majors was Sept. 25, 2011 for the Tigers.
"It's been a long road for him," Redmond said. "For me, it will be fun. I caught a lot of his starts. Seeing him on that mound and me managing him, it's kind of big."