While many of the features that are present in MLB The Show 21 will feel very familiar to veterans of the franchise, there are a number of changes that may take some getting used to. For example, certain players will undoubtedly notice that something is different about adding a fourth pitch in Road to the Show, and some MLB The Show 21 fans may begin to wonder if it is even possible to do so.
To put things simply, all indications suggest that there is currently no way to add a fourth pitch in MLB The Show 21's Road to Show game mode. Indeed, players that have spent several years in the majors, reached very high OVRs, and maximized relationships with their teammates report that they are still not able to equip pitches beyond a third. While this is not definitive confirmation that it is actually impossible to add a fourth pitch, it does seem that the matter has been quite thoroughly explored.
The question then becomes if the inability to add a fourth pitch in this single-player game mode is intended or a bug. At the time of writing, any thing that is said about that would be purely speculative, though it would be a bit surprising to learn that removing this long-standing feature was deliberate. Furthermore, players are currently encountering some other glitches in Road to the Show, which suggests that there are some kinks in the mode that still need to be worked out.
With all of this said, it is worth mentioning that it is still absolutely possible to change pitches in MLB The Show 21. That can be done during bullpen training sessions on days where there is no game on the schedule, and players that are unhappy with their selection of pitches should keep an eye on the options that become available. While changing up pitches may not be quite as good as adding an entirely new one to a ballplayer's arsenal, the feature can be useful none the less.
One final thing to note is that developer San Diego Studios has already indicated that it is planning some Road to the Show changes. Primarily, the outlined changes are focused around ballplayer progression, though perhaps the option to add a fourth pitch will be wrapped into one of these updates. That said, it seems that players will need to get used to having access to only three pitches in the majors for the time being.
MLB The Show 21 is available on PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X/S.