Something about the once-every-few-years pairings of certain teams during interleague play gets me to thinking about how for many years those teams never saw each other except for an occasional meeting in the World Series. Each time there is a new round of interleague series I usually check to see which teams might have met before for the championship. There is nothing significant about the fact these teams met earlier in the World Series, but I enjoy thinking of how different things were before 1997. What follows is a brief description of the World Series history during the first four series of interleague play this year.

Round One, mid-May Six of the 14 matchups involved teams with a World Series history:

Cincinnati Reds at New York Yankees 1939, 1961, 1976 Two wins for Yankees, one for the Reds

Miami (nee Florida) Marlins at Cleveland Indians 1997 Won by the Marlins

Oakland A's at San Francisco Giants 1989 Won by the A's (Also 3 meetings - 1905, 1911, 1913 - between the Philadelphia A's and the New York Giants. Two wins for the A's, one for the Giants.)

Pittsburgh Pirates at Detroit Tigers 1909 Won by the Pirates

Boston Red Sox at Philadelphia Phillies 1915 Won by the Red Sox

Chicago White Sox at Chicago Cubs 1906 Won by the White Sox

Round Two, last weekend Another six of the14 matchups involved teams with a World Series history, three happening since 2000:

Philadelphia Phillies at Baltimore Orioles 1983 Won by the Orioles

Texas Rangers at San Francisco Giants 2010 Won by the Giants

Toronto Blue Jays at Atlanta Braves 1992 Won by the Blue Jays

Detroit Tigers at Cincinnati Reds 1940 Won by the Reds

Houston Astros at Chicago White Sox 2005 Won by the White Sox

New York Mets at New York Yankees 2000 Won by the Yankees

Round Three, earlier this week Only three of the 14 matchups involved teams with a World Series history:

Pittsburgh Pirates at Baltimore Orioles 1971, 1979 Both won by the Pirates

New York Yankees at Atlanta Braves 1996, 1999 Both won by the Yankees (Also two meetings - 1957, 1958 - between the Yankees and the Milwaukee Braves. One win for each.)

Detroit Tigers at Chicago Cubs 1907, 1908, 1945 Two wins for the Cubs, one for the Tigers

(This matchup is significant to the Cubs for two reasons: 1908 is the last year they won the World Series and 1945 is the last year they played in the World Series.)

Round Four, this weekend Four matchups of 14 involve teams with a World Series history:

Philadelphia Phillies at Toronto Blue Jays 1993 Won by the Blue Jays

Boston Red Sox at Chicago Cubs 1918 Won by the Red Sox

Kansas City Royals at St. Louis Cardinals 1985 Won by the Royals

Chicago White Sox at Los Angeles Dodgers 1959 Won by the Dodgers