The Giants designated Wisler for assignment Wednesday after posting a 6.05 ERA, 1.29 WHIP, and 26 strikeouts over 19 1/3 innings this season. However, the right-hander owns a 2.61 ERA over his last nine appearances and fashioned a 1.07 ERA over 25 1/3 innings during the shortened 2020 campaign with the Minnesota Twins.
The 28-year-old is arbitration-eligible this winter.
The Seattle Mariners selected Plassmeyer in the fourth round of the 2018 draft. He was traded to Tampa Bay that same year in a five-player deal involving Mike Zunino and Mallex Smith.
The 24-year-old owns a 3.64 ERA, 1.18 WHIP, and 33 strikeouts in 29 2/3 innings in Double-A this season.