MIAMI — The St. Louis Cardinals added depth to the back half of their bullpen by acquiring veteran left-hander Zach Duke from the Chicago White Sox.

The Cardinals gave up minor league outfielder Charlie Tilson in the deal announced before their game Sunday at Miami.

Duke went 2-0 with a 2.63 ERA for the White Sox this year and leads the American League with 53 appearances.

“The one area we needed to address was the bullpen,” Cardinals general manager John Mozeliak said. “We were fortunate to get somebody of the caliber of Zach Duke. He will fit in ideally.”

Duke is in the second year of a $15 million, three-year contract, which made the trade more appealing, Mozeliak said.

“I was not looking for a rental,” Mozeliak said.

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Since 2014, Duke has appeared in 198 games, which ranks fourth in the majors. He made 169 career starts, all from 2005 to 2013.

The Cardinals become his seventh team, and he’ll join them for the start of their next series Tuesday in Cincinnati. Duke adds depth to a bullpen undermined by the struggles of Trevor Rosenthal, who lost his job as closer and went on the 15-day disabled list Tuesday because of inflammation in his right shoulder.

The 23-year-old Tilson was the Cardinals’ second-round pick in 2011 and is batting .282 this season for Triple-A Memphis. He has a .293 career minor league average in 471 games.

‘’Sometimes you have to make decisions with a steep cost,” Mozeliak said. “Charlie Tilson was someone we were very high on and thought he had some upside, but at some point you have to give up something to get something, and ultimately we feel like we have helped our big league club.”