Let's filter performance in close games into the subset of teams that have made the post-season, and see what we learn about the changes that have occurred over time.
Let's look at just one table of data this time. It's an interesting one. We are comparing the WPCTs in close games for three categories of post-season teams--teams that won the World Series (WSW), teams that lost the World Series (WSL), and teams that made the post-season but didn't make it to the World Series (NWS).
You can pretty much throw a blanket over World Series winners and losers in terms of their WPCTs--whether in close games or overall. Their values--and their percentage differential (in the rightmost section of the chart, highlighted in green)--are virtually identical.
These percentage differentials are neither large nor small in the scheme of things. What's most notable about them, however, is how they've been shrinking over time.
Teams are underperforming in close games relative to their overall WPCT to a markedly lesser extent as the multiple-round post-season has taken hold and expanded. The differential that was in place through 1968 has halved over the past twenty years (1993-2012).
What's happening is that overall WPCTs are falling faster than WPCTs in close games.
We'll look at some detailed "scatter charts" next time around, and see something rather astonishing that's happening in the midst of all this tightening of the difference between WPCTs in close games and overall WPCTs for post-season teams.