Shaw elected to become a free agent Thursday, Greg Johns of MLB.com reports.
Shaw was outrighted to the Mariners' alternate training site in August, and he'll opt to search for a new organization ahead of the 2021 season. The right-hander has struggled over the past three seasons as he carries a 6.17 ERA and 1.62 WHIP over 132.2 innings with the Rockies and Mariners.