MLB use of 6 man crews for the playoffs

[Manny A]

Originally Posted by Dakota

Will whatever benefits there are of having U5 and U6 go away (or become even a net negative) once instant replay use is expanded? In other words, if they are going to review the calls that are in doubt anyway, why have the larger crew?

Don't forget that the expanded use of IR starting next season (if passed by owners, the players association, and the umpires association) is still limited by the number of challenges a manager will be allowed during a game. In theory, a manager could run out of challenges, and then there's a situation that requires a judgment call by the LFU or RFU. I would agree with you if managers were allowed unlimited challenges.

As a side, who came up with "U5" and "U6" as designations for these umpires anyway? Why not "U4" and "U5", since there is no such thing as "U4" in a four-man crew?