How about a comp with third baseman Pablo Sandoval, who in 2008 made his 41-game MLB debut in his age 21 season?
Through their first two MLB seasons Sandoval and Rafael Devers posted these numbers:
PS 194 G, 633 PA, .333/.381/.543/.924, OPS+ 139, 5.4 bWAR, 6.1 fWAR
RD 179 G, 730 PA, .254/.311/.449/.760, OPS+ 100, 1.3 bWAR, 1.7 fWAR
Those first two seasons Sandoval played 132 games at third base, 43 at first base and 14 at catcher.
https://www.fangraphs.com/statss.aspx?playerid=5409&position=3B#fielding
A wide range of outcomes is possible for a 22-year-old who is difficult to project. Rafael Devers could become a perennial All Star or fall short of that status.