Walter was added to Boston's 40-man roster Tuesday, Christopher Smith of The Springfield Republican reports.
The 26-year-old southpaw dominated in nine starts at Double-A (2.88 ERA, 68:3 K:BB in 50 innings) before struggling in two starts at Triple-A and missing the rest of the season with a neck strain. He has resumed throwing and should be ready for spring training. If Walter regains his form from Double-A, he could pitch in the big-league rotation in 2023.