Aren't the rules that putting a positional player on the IL requires him to be replaced by a positional player? That was my impression at least. Agree that if Irvin were available he should have gotten the nod, just not sure what the nuances of the rules are.
As far as I can tell, the rule is only regarding the max number of positional and pitchers that can be rostered, but not specifically that like must replace like. So as long as they made another move before the game that got them within the correct limits, they'd have been good. We've seen this happen already this year previously. So they know the rules and knew Irvin was an option and decided against it. I do understand the rationale for going with the bullpen game given the status of the relievers and the pending off day. I still would've preferred going to Irvin, but I didn't think it was an indefensible decision. It did, however, blow up in their faces so blame can be slung fairly, IMO.
In the postseason, if you're gonna replace someone on your roster for a given round due to an injury, then you can only replace the injured player with the same type of replacement.