Mayer receives $6.664 million, which is the full slot value for the No. 4 overall selection. This should be considered a big win for Boston, who can now go over slot for Jud Fabian and Nathan Hickey. Mayer was considered the top prospect in the 2021 class, and he's already a top-40 minor league talent in the eyes of many evaluators. Mayer comes in at No. 31 in Brendan Tuma's latest Top 100 prospect rankings.