I think Casas' career might have died.
To me Sox management is stupidly, nastily making a big deal out of replacing the worst player (WAR -0.8) on the team. Gonzalez has much better numbers than Casas had--problem solved.
In Devers defense, we can already see the possibility that his hitting will be better than ever if only because he is less likely to get hurt. Think Ortiz or JDM, both of whom were keys to winning 4 WS.
Also in Devers defense, the simple fact is that all three positions--3B, fulltime DH, and 1B--require some adjustments. So in fact the Sox player with the biggest salary is being jerked around by management.
If they want to move him to 1b, fine, but do it next year and give him a whole spring training to make the adjustment.