As a freshman, Fletcher started 56 games in centerfield and hit .291 with 64 hits, 12 home runs, and 37 RBIs, earning freshman All-American honors from the National Collegiate Baseball Writers Association and Baseball America, and the Southeastern Conference All-Freshman Team.

[5] Fletcher signed with Arizona and made his professional debut with the Kane County Cougars of the Single–A Midwest League.

[8] Fletcher was assigned to the Amarillo Sod Poodles of the Double-A South for the 2021 season and slashed .264/.314/.445 with 15 home runs and 56 RBIs over 102 games.

[13] On November 15, 2022, the Diamondbacks selected Fletcher's contract and added him to the 40-man roster to protect him from the Rule 5 draft.

On April 30, Fletcher was promoted to the major leagues for the first time after Corbin Carroll suffered a left knee contusion.