By Bruce Levine–

CHICAGO (CBS) — In win-now mode and looking to strengthen their rotation, the White Sox have acquired Padres right-hander James Shields. In return, San Diego will receive minor league propsects Erik Johnson and Fernando Tatis Jr. and rid themselves of some of the economic burden on the 34-year-old Shields’ deal.

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Shields has nearly $58 million left on a deal that runs through 2018. The White Sox will be responsible for about $26 million of that remaining amount, with the Padres retaining more than $30 million on the deal, a source said. Shields does have an opt-out clause after the 2016 and 2017 seasons. Shields is owed $21 million in 2017 and $21 million in 2018, with a club option for 2019.

The White Sox had previously rebuffed the Padres’ interest in shortstop Tim Anderson, Chicago’s top prospect, sources told 670 The Score.

Shields is 2-7 with a 4.28 ERA and 1.42 WHIP this season. His ERA sat at 3.06 before he had a disastrous start recently in which he allowed 10 earned runs in 2 2/3 innings.

Shields is a significant upgrade in a rotation that’s struggled to find consistency on the back end, and he’ll likely fit in the rotation between the White Sox’s two left-handed aces, Chris Sale and Jose Quintana. Shields has also been remarkably durable in his career, throwing at least 200 innings in nine straight seasons, the longest streak in the majors.

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“We’re pleased to add a starter of James Shields’ caliber to our starting rotation,” White Sox general manager Rick Hahn said in a statement. “We believe this move makes the entire pitching staff stronger, and the club certainly benefits from his addition in terms of pitching depth and quality. He has proven to be one of the most dependable and durable pitchers in the major leagues over his career.”

Shields has a lifetime 3.76 ERA. He also has his share of postseason experience, having made 11 playoff starts, including four in 2014 when he helped the Royals reach the World Series, where they fell in seven games.

The 2015 International League Pitcher of the Year, the right-hander Johnson, 26, has spent most of 2016 at Triple-A Charlotte, where he was 2-1 with a 2.94 ERA. He struggled in two starts at the big league level, compiling a 6.94 ERA for the White Sox this season.

The 17-year-old Tatis is the son of former MLB third baseman Fernando Tatis.

The White Sox — who have emphasized that they’re looking at a two-year window to compete with their current roster — have excess money with the sudden retirement of Adam LaRoche in spring training freeing up $13 million to use toward Shields contract. Projecting out further, John Danks’ $14.25 million comes off the books after 2016. He was released in early May.

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Bruce Levine covers the Cubs and White Sox for 670 The Score and CBSChicago.com. Follow him on Twitter @MLBBruceLevine.