On January 31, 2014, Hammel signed a one-year, $6 million contract with the Chicago Cubs [REF].
On July 4, 2014, the Cubs traded Hammel, along with pitcher Jeff Samardzija, to the Oakland Athletics in exchange for top shortstop prospect Addison Russell, pitcher Dan Straily, outfielder Billy McKinney, and a player to be named later [REF].