Walden was designated for assignment by the Red Sox on Wednesday.
The right-hander was removed from the 40-man roster to make room for the signing of Marwin Gonzalez. Walden appeared in 15 games during 2020 and surrendered 23 hits and 14 earned runs with a 10:9 K:BB over 13.1 innings. The 32-year-old had a 3.79 ERA and 1.19 WHIP over the previous two seasons, so he could still make his way back to the majors in 2021.