In the game one matchups for the National League and American League division playoffs, the Chicago Cubs v. Los Angeles Dodgers game drew the largest TV audience: nearly 5.4 million viewers.

Game
Network
Viewers P2+

CUBS- DODGERS
TBSC
5,381,000

RED SOX-ANGELS
TBSC
4,442,000

BREWERS-PHILLIES
TBSC
2,764,000

WHITE SOX-RAYS
TBSC
2,610,000

Source: The Nielsen Company (October 3, 2008).

This week begins Major League Baseball playoffs in the National League (Philadelphia Phillies vs. Milwaukee Brewers and Los Angeles Dodgers vs. Chicago Cubs) and American League (Boston Red Sox vs. Los Angeles Angels and Chicago White Sox vs. Tampa Bay Rays).
Historically, at least where league championship series are involved, ratings have been significantly higher when teams from major markets, such as Chicago, Boston and Los Angeles, are involved. A breakdown of those matchups will be featured prior to the upcoming NL and AL championship series.
Below are historical ratings since 2000 …