Law of Averages at its finest in this four-game series. Before you respond with "those first three games have no bearing on an undisclosed betting outcome to the players in the final game," let me just tell you that the Law of Averages works a lot more than you think.
It does not guarantee anything, obviously, but it does indicate a higher percentage play going against the grain based on what has happened in unlikely fashion. In other words, there's a very high chance that the under does not hit four games in a row, especially when it's a series that involves arguably the most explosive offense in all of baseball, nor does it indicate that the Athletics will actually sweep a four-game series with the storied Yankees franchise. If you were to take both of these bets, I would actually go as far as guaranteeing that you push as the absolute worst case scenario, meaning you can only win (Or only lose the extra juice if you go 1-1). Both the over and Yankees ML look like very good bets with this method... doesn't always work, but trust me, it works most of the time, especially in a sport like baseball where everything is about averages. If I could quote Los Angeles Clippers play-by-play announcer Ralph Lawler, "It's... the Law."