The Padres receive right-handed pitcher Erik Johnson and infielder Fernando Tatis Jr. in exchange for Shields and cash in return. Chicago refused to part with shortstop Tim Anderson, their top prospect, per Jon Heyman.
The White Sox entered Saturday at 29-26, 1½ games out of first place in the American League Central, though they are just 2-8 in their last 10 games.
San Diego is expected roughly $31 million of the remaining left on Shields' contract, per Ken Rosenthal of Fox Sports.
With 120 days remaining in the season, there is roughly $13.8 million remaining of Shields' $21 million salary in 2016, then he is due $21 million in both 2017 and 2018, per Cot's Contracts. Shields also has a $16 million club option for 2019 that includes a $2 million buyout, meaning there is roughly $57.8 million in guaranteed money left on his contract.
Shields was signed by San Diego in their whirlwind offseason heading into the 2015 season to a four-year, $75 million deal, and he was expected to be the ace of a team that had designs on contending. Both have failed to live up to their roles to date, with the Padres following an 88-loss season in 2015 with a last-place standing this year, currently 22-34.
Shields has been a workhorse for San Diego but the results aren't quite up to his previous performance. He started 33 games and pitched 202⅓ innings in 2015, his ninth-straight season with at least 200 innings, but his 3.91 ERA and 94 ERA+ were his worst figures since 2010, after averaging 233 innings with a 3.17 ERA and 124 ERA+ from 2011-2014 with the Tampa Bay Rays and Kansas City Royals.
In 2016, Shields is 2-7 with a 4.28 ERA in 11 starts, the latter number inflated by allowing 10 runs in a disaster start at Seattle on Tuesday.
After that game, a 16-4 loss, Padres CEO Ron Fowler unloaded on the team on a local radio station, and called out Shields specifically, saying "To have a starter like Shields to perform as poorly as he did yesterday I think is an embarrassment to the team and an embarrassment to him. It's about as frustrating as it can get but we've got to get through."
Shields took the high road in his response to Fowler's comments on Wednesday.
"I guess I shouldn't have given up 10 runs. I guess I was the guy. I'm sure it was more about the frustration of our team losing. I'm frustrated myself. Obviously, I'm not happy with my game. I don't know if it's an 'embarrassment' to me, but I'm not happy with it," Shields said, per the San Diego Union-Tribune. "He can say it on the radio, but we're just as frustrated in this clubhouse."
Shields adds depth to a White Sox rotation already strong at the top with Chris Sale and Jose Quintana. Those two are fourth and first, respectively, in the American League in ERA, combining for a 2.21 ERA in 22 starts and 150⅔ innings entering Saturday. The rest of Chicago's starting staff has a collective 4.73 ERA in 33 starts and 186⅓ innings this season.
Johnson is a 26-year-old pitcher who has made two starts for the White Sox this season. He also had eight starts in Triple-A with a 2-1 record and a 2.94 ERA. He had 35 strikeouts and 17 walks. He is a former second-round selection from the University of California, Berkeley in 2011.
Tatis Jr. is a 17-year-old from the Dominican Republic who signed with the White Sox as an international free agent in 2015. He has not made his big league debut yet. Tatis Jr. is the son of former Major Leaguer Fernando Tatis, who played 11 years for various teams.