CHICAGO -- When Theo Epstein first joined the Chicago Cubs as the team's president in 2011, he said every chance to win would be considered sacred.

But even with the Cubs maintaining a healthy lead in the National League's Central Division, Epstein knows he can't afford to take anything for granted. So when the Cubs traded for what Epstein called a "game-changer" in highly sought-after closer Aroldis Chapman from the New York Yankees Monday, Epstein said it improved the Cubs' chances of capturing a World Series title this fall.

"The goal is to win three postseason series and that's not an easy thing to do," Epstein said. "You need dynamic players and we felt like we could really benefit from an elite talent -- a game-changing type pitcher like Aroldis Chapman."

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In 31.1 innings this season with the Yankees, Chapman has converted 20 of 21 save opportunities and has posted a 2.01 ERA with 44 strikeouts.

Chapman is set to join the Cubs Tuesday before his new team faces its crosstown rivals, the Chicago White Sox, in the second of a four-game series. Kyle Hendricks (9-6) will start for the Cubs and will face James Shields (4-12).

The Cubs' bullpen was a high priority heading into next week's trade deadline and Epstein believes adding Chapman will be a positive add-on moving forward.

"I cannot wait to take the mound a Wrigley Field and look forward to helping my teammates deliver a championship to Chicago," Chapman said in a statement Monday that also expressed regret for his role in a domestic violence incident that led to a 30-game suspension.

Cubs manager Joe Maddon hasn't yet decided how adding Chapman to the Cubs' bullpen would impact his staff of relief pitchers. Maddon said each would be bumped up an inning, including current closer Hector Rondon.

"In the sixth, seventh and eighth (innings), it really opens things up," Maddon said. "... (Chapman) is a unique pitcher, he's unique with his ability to throw the ball that hard regularly."

The White Sox have already seen Chapman in May when Chapman picked up his second and third saves. Manager Robin Ventura said in a series that already has a lot of build-up due to the in-town rivalry, his hitters will know what to expect.

"He's tough -- he throws hard," Ventura said Monday. "It's a live arm and it's a nice addition to have. We'll definitely have to turn it up when he's pitching."

Ventura said the White Sox have "already moved on" from an incident involving Chris Sale, who will start in the series finale Thursday at Wrigley Field. Sale was suspended for five days after cutting up 1976 throwback jerseys the White Sox were to have worn on Saturday when Sale was scheduled to pitch.

The incident won't impact how the White Sox compete against the Cubs, Ventura said.

"Guys have seen a lot of stuff and it's about playing," Ventura said. "I think they're about playing and we'll go with that until something needs to be addressed. As far as playing, guys are just moving on and playing."