He began 2014 as a hardluck pitcher. He set a major league record for lowest ERA (1.46) by a winless pitcher through his first 10 starts. The 1.46 ERA was the latest league-leading ERA by a winless pitcher since Bruce Sutter's 0.89 ERA on June 7, 1977. Samardzija won his eleventh start of the season by striking out a season-high 10 San Francisco Giants. On June 18, 2014, the Cubs offered Samardzija a five-year, club friendly deal that included multiple option years, which he rejected.
On July 6, 2014, he was revealed as a National League All-Star, but was not eligible to play because he was traded to an American League team.
On July 5, 2014, Samardzija, along with Jason Hammel, was traded to the Oakland Athletics in exchange for top shortstop Addison Russell, pitcher Dan Straily, outfielder Billy McKinney, and cash. In his debut on July 6, he went seven innings with five strikeouts, allowing one run and four hits.
On December 9, 2014, the Athletics traded Samardzija along with Michael Ynoa to the Chicago White Sox in exchange for Marcus Semien, Chris Bassitt, Rangel Ravelo and Josh Phegley. Samardzija and the White Sox avoided arbitration by agreeing to a one-year deal for $9.8 million on January 16, 2015.