How Would Realignment Affect Playoff Races?

Over the weekend Buster Olney reported that Major League Baseball and the players’ union discussed a possible plan for realignment. The plan would move the Houston Astros, or possibly the Florida Marlins, to the AL so that both leagues would have 15 teams; eliminate the three divisions within each league; have the top-five teams from each league go to the playoffs; and require an inter-league game every day (because of the odd number of teams in each league). There is lots to consider with such a realignment — fairness, logistics, etc. — but I wanted to look at a single aspect: how will this plan would affect the number of competitive playoff races at the end of the season?

With the top-five teams in each league making the playoffs, instead of three division leaders and a wild card, the playoff picture would change. Would this mean more or fewer competitive races at the end of the regular season? To quantify this I counted the number of playoff teams that wouldn’t have made the playoff if they had won three fewer games, and then counted the number of non-playoff teams that would have made the playoffs if they had won three more games. Though not perfect, I think this is a good proxy for the “end-of-season” excitement. I counted this number under the current alignment and under the realigned leagues.

Here, as an example, is the AL from last year. Teams in italics made the playoffs and bolded teams met my “competitve-race” criterion.

AL East AL Central AL West
Tampa Bay Rays 96 Minnesota Twins 94 Texas Rangers 90
New York Yankees 95 Chicago White Sox 88 Oakland Athletics 81
Boston Red Sox 89 Detroit Tigers 81 Los Angeles Angels 80
Toronto Blue Jays 85 Cleveland Indians 69 Seattle Mariners 61
Baltimore Orioles 66 Kansas City Royals 67

In this case I get zero competitive teams. If either the Rays or Yankees won three fewer games they still would have made the playoffs since the Wild Card saves them. Here are the same wins under the realigned system, with the Astros included.

Tampa Bay Rays 96
New York Yankees 95
Minnesota Twins 94
Texas Rangers 90
Boston Red Sox 89
Chicago White Sox 88
Toronto Blue Jays 85
Oakland Athletics 81
Detroit Tigers 81
Los Angeles Angels 80
Houston Astros 76
Cleveland Indians 69
Baltimore Orioles 66
Kansas City Royals 67
Seattle Mariners 61

Under the new system the same four teams would have made the playoffs, but they would have been joined by the Red Sox. Here, though, there are now three teams that meet my competitive-race criterion. Three fewer wins for the Rangers or Red Sox pushes them out of the playoffs and three more from the White Sox puts them in.

Doing the same for all the years back to 1995:

Year AL Current AL Realigned NL Current NL Realigned
1995 3 4 3 2
1996 4 5 3 0
1997 0 3 2 0
1998 2 4 3 0
1999 0 0 3 0
2000 5 2 0 3
2001 0 0 3 0
2002 0 3 2 0
2003 3 2 2 6
2004 3 5 4 3
2005 2 3 3 5
2006 0 3 6 2
2007 0 2 7 2
2008 2 5 5 3
2009 2 5 0 3
2010 0 3 3 0
Average 1.63 3.06 3.25 2.13

Over the past 15 years this new system would have made the AL almost twice as competitive and the NL about a third less competitive. Overall an extra 0.3 teams would be in a competitive race per year. So the realignment would have slightly, but not drastically, increased the number of teams in the playoff hunt. Although it would change which teams were in the hunt, the new system would make it easier for teams from good division, e.g. the AL East, to make the playoffs.

Dave Allen's other baseball work can be found at Baseball Analysts.

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if it’s easy to do (which I’m guessing it is), it’d be interesting/useful to see if the results are essentially the same, or different, when close = 2, 4 or 5 GB.