So baseball's 2015 regular season is over and we have our 10 postseason teams, and in a short series anything goes. But I‘ve often wondered what would’ve happened if baseball hadn't changed to a playoff format in 1969, and the team with the best record in each league continued to meet in the World Series.

This year we would get the Show Me Series: the St. Louis Cardinals (100-62) vs. the Kanas City Royals (95-67), 1985 Redux. AKA, the “Take Pity on Don Denkinger” Series.

We still might get it. But how likely is it? How often do the teams with the best records in each league meet in the World Series?

I'm glad you asked: 

For the first three years, it was a wash. Same same. Then divergence. If it seems the divergence got worse, it did, because the playoffs became more complex: from best-of-five LDS until 1984, to best-of-seven LDS until 1993, to a two-tiered playoffs with wild card that we have today.

But back to the question: How likely is it for a team with the best record in its league to make the World Series?

• Best-of-five LCS (1969-1984): 56%
• Best-of-seven LCS (1985-1993): 61%
• Wild card era: best-of-five LDS, then a best-of-seven LCS (1995-present): 32%

Some observations:

• The Braves have suffered the most from the playoff format. They had the best record in the NL nine times but only went to the World Series five times, for a deficit of 4. 
• Cubs and Pirates also suffered. Both have deficits of 3. That's right: in a non-playoff format, the Cubbies would‘ve gone to the World Series three times in the last 30-odd years: in ’84, ‘89 and ’08.
• The Giants have benefitted most from the playoff format: best record once (in 2000, when they lost to the Mets in the LDS), but five World Series appearances for a net gain of 4. 
• The Yankees have a deficit of 1, so they'd have 41 pennants rather than 40. Also their period of domination would‘ve been more recent. No pennants in ’96, ‘00 or ’01, but pennants in 2006, ‘11 and ’12.
• The two teams that have never been to the Series (the Mariners and Nats), each would‘ve gone (’01 and last year), but now four teams would be no shows, since they‘re all post-’68 teams that have never had the best record in their league: Rockies, Marlins, Padres and Rangers. 

We would‘ve gotten Royals/Phillies in ’77 rather than ‘80. The Braves wouldn’t have gone in ‘91 but would’ve gone in every subsequent year in the decade, plus ‘02 and ’03. In 2000, the Yankees/Mets subway series would‘ve been replaced by the White Sox/Giants series, but would’ve reemerged in ‘06.

Certain teams seem to do particularly well when they have the best record. The BoSox led the AL in wins three times, and each of those times (’86, ‘07, ’13) they won the pennant. And good news for Cardinals fans: Six times they‘ve had the best record in the NL and five of those times they made the Fall Classic (2005 was the misstep).

But overall the playoff format seems tailor-made for upstarts. It’s October 5, 2015, and a whole new season. 

Who could forget the great Cubs-A's World Series of 1989?