[9][10] Massey made his professional debut with the Burlington Royals of the Rookie-level Appalachian League, batting .272 with five home runs and 25 RBIs over 42 games.

[12] Massey spent the 2021 season with the Quad Cities River Bandits of the High-A Central with whom he slashed .289/.351/.531 with 21 home runs, 87 RBIs, and 27 doubles over 99 games.

[18] He made his MLB debut the next night as a pinch-hitter versus the Toronto Blue Jays at Rogers Centre, striking out in his only at-bat.

[19] He made his first major league start on July 16 versus the Blue Jays and recorded his first MLB hit, a single off of Max Castillo, in his first at-bat.

[20] He was optioned back to the minors on July 18, and called up to the major leagues once again on August 3 following the trade of starting second baseman Whit Merrifield.