Arroyo cleared waivers and was outrighted to Boston's alternate camp in Pawtucket, Pete Abraham of The Boston Globe reports.
Arroyo spent just one day on the 28-man roster prior to being designated for assignment by the Red Sox, but he'll head to the alternate training site after clearing waivers. The 25-year-old hit .229 with seven RBI and 18 strikeouts over 50 at-bats with the Rays last year.