The Cubs promoted Caissie from the rookie-level Arizona Complex League to Low-A Myrtle Beach on Tuesday.
Caissie, who was the 45th overall pick in the 2020 first-year player draft and one of the prospects the Cubs acquired from the Padres this winter in the Yu Darvish trade, will get his first taste of full-season ball over the final month of the 2021 campaign. The 19-year-old received the promotion after slashing a blistering .345/.474/.591 in 137 plate appearances against overmatched competition in the ACL.