Chafin declined his portion of his $5.25 million mutual option with the A's on Thursday, making him a free agent Jon Heyman of MLB Network reports.
Chafin had a career-best season with the Cubs and Athletics in 2021 with a 1.83 ERA and 0.93 WHIP in 68.2 innings across 71 appearances. He'll have the chance to earn a payday during the offseason and is a candidate to serve as a high-leverage reliever in 2022 if his results continue.