Why the New Instant Replay Rule in Major League Baseball is Unfair

Yesterday the instant replay rule was introduced in Major League Baseball in order to correct a home run hit by the New York Yankees' Alex Rodriguez. There has been much debate about whether baseball should start using the instant replay or not. My issue isn't whether there should be an instant replay or not, I'm fine either way, my issue is with the timing of introducing the instant replay because it isn't fair to every team in Major League Baseball.

The reason that the new instant replay rule is not fair is because the rule was changed in the middle of the season. When has a rule in sports ever changed during the season? It doesn't happen. Even if there is a new rule that is for the safety of the players on the field, like the new rule for third base coaches wearing helmets, it is decided during the offseason and introduced at the beginning of a new season.

When balks were introduced for the first time was it introduced half way through the season? Was runner interference created halfway through a game in August? Was the ground rule double just created on a whim one July afternoon?

How come some teams are going to get possible game winning home runs reversed for the next month but teams at the beginning of the season won't? What if a team wins a division by one game and they had a game winning home run reversed? And what if the team that lost by one game had a game winning home run before the rule that wasn't reversed? The chances of this happening are unlikely but it doesn't change the fact that it would be pretty lame for a team to lose a spot in the playoffs because Major League Baseball decided to change the rules during the season.