There is no such thing as an "upset" in baseball. On any given day, the worst team in the major leagues beating the best one isn't particularly news. It's a proverb that every team wins a third of its games and loses a third; that what separates the best team from the worse one is what they do in the remaining third.
It follows that no playoff system, no matter how extended, is as good a test as the regular season. There is a reason why there are 162 games in a baseball season and only 16 in a football season!
It used to be that the nation would come to a halt for a week every year when the team that had clearly demonstrated its superiority over the National League played a best-of-seven series against the team that had done the same over the American. Kids in cities whose teams weren't even playing hollowed out books with razor blades so they could hide transistor radios and listen to every pitch in school. Now, with a playoff system that's a month or so long and second chances given to two teams in each league that weren't even good enough to win their own divisions, it barely produces more than a national yawn.