Yoenis Céspedes
On July 31, 2014, Lester and Jonny Gomes were traded to the Oakland Athletics for Yoenis Céspedes and a competitive round 2015 draft pick. The move reunited Lester with former teammates Jed Lowrie, Coco Crisp, Brandon Moss and Josh Reddick. He won his debut start against the Kansas City Royals on August 2. He had a 6–4 record and a 2.35 ERA, while pitching for the A's.