This from ESPN:
ESPN’s Sunday Night Baseball telecast featuring the Boston Red Sox and the New York Yankees delivered an average of 4,698,000 viewers and 3,427,000 households to become the most-viewed MLB game on the network since June 3, 2007.
The corresponding 3.5 rating was the highest since the Yankees and Red Sox equaled the number September 16, 2007. ESPN’s telecast was the most viewed of the four-game series, outperforming the closest telecast by 19 percent among viewers, and the most-viewed MLB regular season game to date in 2009 (cable or broadcast).
The Yankees defeated the Red Sox 5-2 to complete a four-game sweep at Yankee Stadium. The telecast generated a 12.3 metered market rating in Boston and a 10.3 in New York.