Petit appeared in 23 games for the D-backs last season, going 3-10 with a 5.82 ERA, including a 3-9 mark and 5.72 ERA in 17 starts. He struck out 71 batters in 83 1/3 innings.
Originally signed by the Mets as a non-drafted free agent in 2001, Petit was traded to the Marlins following the 2005 season as part of the deal that sent Carlos Delgado to New York.
Petit was dealt to the D-backs in '07 for right-hander Jorge Julio.
During his Major League career, Petit has a 10-20 record and 5.72 ERA in 71 appearances, including 36 starts.
The Mariners currently have 36 players on their 40-man roster, including 20 pitchers.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.