• The American League Wild Card game between the New York Yankees and Boston Red Sox peaked at 8.4 million viewers on Tuesday night.
• It's the most number of people to watch a baseball game on ESPN since 1998.
• The Red Sox beat the Yankees 6-2 and advanced to the AL Division Series to play the Tampa Bay Rays.

The New York Yankees and Boston Red Sox kicked off the 2021 postseason on Tuesday with the most-watched baseball game on Disney's ESPN networks since the day Mark McGwire hit his then record-tying 61st home run in the 1998 season.

The American League Wild Card game pitted the long-time AL East rivals against one another in an elimination context. The Red Sox beat the Yankees 6-2 and advanced to the AL Division Series to face the Tampa Bay Rays. Game one of the best-of-five set starts Thursday.

An average of 7.7 million viewers across ESPN platforms watched Tuesday night's contest, and the network said viewership peaked at 8.4 million between around 10:15 p.m. and 10:30 p.m. ET.

That's the most since Sept. 7, 1998, when McGwire's St. Louis Cardinals faced Sammy Sosa's Chicago Cubs in a late-season contest. While neither team made the playoffs, all eyes were on the series, because McGwire and Sosa were both on pace to pass Roger Maris' single-season home run record of 61 in 1961.

McGwire hit his 61st that night in front of an ESPN audience of 10.6 million. He finished the season with 70 home runs, followed by Sosa at 66.

ESPN said the Boston area drew a 19.8 household rating for Tuesday's contest. That means nearly 20% of all TVs in that market, which has 2.3 million households, were tuned into the game. Among Boston viewers, it was the most-watched Red Sox game on ESPN since 2009.

The New York market registered an 11.2 household rating. ESPN used metrics from Nielsen to gauge viewership.

Advertising data firm EDO estimated that search engagement for Tuesday's Wild Card was 55% higher than the average 2021 MLB regular season game featuring either of the clubs. Viewers were 55% more likely to search online for a brand in the minutes after its commercial aired during the game. Nissan and Verizon were among the most-searched brands, EDO said.

Viewership for the Yankees-Red Sox game was up 67% from the 2019 AL Wild Card game between the Rays and Oakland Athletics. That contest drew 4.6 million viewers.

For Wild Card games across all networks, the 2015 National League contest between the Chicago Cubs and Pittsburgh Pirates still has the biggest audience, as 8.3 million viewers tuned in on WarnerMedia's TBS network.

Tuesday night's game is second, followed by the 2015 AL Wild Card on ESPN, which lured 7.6 million viewers to see the Houston Astros play the Yankees. The 2016 NL Wild Card game, pitting the New York Mets against the San Francisco Giants is fourth at 7.4 million.

MLB could be for another big hit on Wednesday as the Cardinals and Los Angeles Dodgers face off in the NL Wild Card game. That game is on TBS, with viewership information likely to be available on Thursday.

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