Prior signed a one-year deal worth $1 million last December with San Diego, passing up higher offers in both length of contract and base salary to play for his hometown team.
Prior, who hasn't pitched in the Major Leagues since 2006, had shoulder surgery in June to fix a torn anterior capsule in his right shoulder.
The Padres team doctors who performed the surgery said the capsule in Prior's shoulder had torn away from the humerus bone. The injury, according to Dr. Jan Fronek, is often associated with "traumatic events, usually from a fall."
At the time of the surgery, Prior was 13 months removed from arthroscopic surgery on the same shoulder, though Dr. Heinz Hoenecke said that surgery was successful and this tear was unrelated.
"He feels really good right now," Prior's agent, John Boggs, said recently. "He is at the beginning stages of his rehabilitation. He's playing catch, but he's not at the point where he's airing it out yet."
At the time of the surgery in June, Fronek indicated that Prior could "optimistically" be throwing again by spring.
Prior, who is from San Diego and still makes his home there, told Boggs that he would like to pitch for the Padres, though general manager Kevin Towers said the team would likely only be interested in a Minor League contract.
"We would definitely be interested in the Padres," Boggs said. "It's a situation where I'm sure he would love the opportunity to come back with the Padres.
"But [the Padres] will have to express interest. Hopefully they're interested in us. We're interested in any team that has reciprocal interest in Mark."
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.