Freeman's advice is good, but the thing to keep in mind is that the most important thing in the playoffs is luck. Sure, having the best team in the playoffs can improve your odds of winning, but only slightly. It's one of the more frustrating aspects of this game. However, it's not unlike real life where any team can win. For example, I still remember the Mets beating a vastly superior Orioles team in the 1969 World Series*.
Here's anecdotal evidence from my own experience of how much luck plays a part.
I have had three 100+ game winners. One made it to the finals and lost. The other two were eliminated in the semi-finals.
I defeated the best team I ever saw in the semi-finals. They had an amazing 119-43 record (.735 pct) and a +289 run differential. Of course back then, it was even more luck dependent; semi-finals used to be a best-of-five series.
I have played thirty 90s teams with a respectable .531 winning percentage. My overall winning percentage in all playoff games (for all my teams) is .530. I made the playoffs 13 times in the 90s. Yet I have never won a single 90s championship.
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Hang in there. For me, the meat of the game is the regular season where you are fighting for a winning record, a positive run differential, and, most importantly, a playoff spot. If you've done that, you've done your job. Now you have a chance to roll the playoff dice and hope you get lucky. Play well, and the elusive championship will eventually come.
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If anyone's interested, here's a link to that monster team, managed by AdamKatz, that I beat many years ago:
https://365.strat-o-matic.com/team/405903==========
*
https://en.wikipedia.org/wiki/1969_World_Series==========
My SOM365 record:
https://365.strat-o-matic.com/member/10770207