For the first time in a couple years, the Yankees are playing in an ultra-important series to end the regular season. The last time that they had genuinely major stakes this late was probably 2012, when they went into the final three games tied with the Orioles atop the AL East. The Yankees swept their final series while Baltimore dropped two of three, giving the Yankees a final two-game cushion.
Considering how often the Yankees have been contenders over their long history, there are plenty of examples of them playing in an important final series.