The Cubs -- who signed Jackson to a four-year deal before the 2013 season -- will pay the majority of Jackson's contract, with the Padres paying him the pro-rated minimum.
"In a sense, you're getting a veteran player at league minimum," said Padres manager Andy Green, who was speaking only about the possibility of signing Jackson at the time. "So those are always enticing pieces to have to stabilize you at times."
The Padres' rotation has grown thin recently, with their recent trade of James Shields to the White Sox, as well as injuries to Andrew Cashner (strained neck), Tyson Ross (right-shoulder inflammation), Robbie Erlin (Tommy John surgery) and Cesar Vargas (flexor strain in right elbow).
"You never know how many pitchers you're going to need, especially starters," said Green. "It's not the rotation we thought we'd be looking at in the middle of June. Depth is very necessary."
Spring Training roster projections are almost always a fool's errand, and the Padres' starting rotation is exhibit A.
There was a point in mid-March when projections had San Diego's starting five as: Ross, Shields, Cashner, Erlin and Brandon Maurer -- who is currently in the bullpen. Obviously, none of those five help comprise the current rotation.
It's unclear where Jackson will begin in the Padres' organization, but he hasn't pitched since May 30 with Miami. He was released five days later.
Jackson signed a four-year deal with the Cubs worth $52 million in December 2012. He was coming off a four-season stretch in which he went 45-41 with a 3.98 ERA. His best season came with Detroit in '09, when he posted a 3.62 ERA with 161 strikeouts and was named to the All-Star team.
But Jackson struggled mightily with Chicago and was released last season. The Padres spoke with Jackson during the offseason, but never offered him a contract.
"I talked to him on the phone a few times about the possibilities here," said Green. "I don't know that we ever got to a point where we ever offered him anything, but he was in our conversation in the offseason."