Prior went to spring training on a minor league contract. He had a 4.66 ERA in seven relief appearances for Triple-A Louisville, but last pitched April 21 because of a right shoulder strain.
The 32-year-old Prior last pitched in the majors in 2006, a year before reconstructive shoulder surgery. He's also pitched in the Texas, Boston and New York Yankees' minor league systems.
Reds manager Dusty Baker was Prior's manager with the Chicago Cubs from 2004-06. Prior told Baker he was treated excellent and will go home, rest and maybe try again depending "on if his arm comes back"
Baker said Friday he was hoping Prior could help the Reds this season.