This weekend, an e-sports version of March Madness gets underway on Alphabet's (GOOGL) - Get Report YouTube

Google is the exclusive streaming platform for FaceIt's Esports Championship Series, in which gamers test their shooting skills off the hardwood in the multi-player battle game Counter-Strike: Global Offensive.

Though e-sports is a nascent market, Google and Amazon (AMZN) - Get Report take gamers seriously. Google's YouTube launched the YouTube Gaming app in 2015, and Amazon spent close to $1 billion for game streaming outfit Twitch in 2014. Facebook (FB) - Get Report has stirrings with a deal with Activision (ATVI) - Get Report , and could take a bigger role.

"Amazon and Google are already an early beneficiaries of the ad dollar flow into eSports media due to their ownership of Twitch and YouTube, respectively," Macquarie analyst Ben Schachter wrote in a report on the gaming face off.

E-sports sponsorships, advertising, prize money, betting, ticketing, merchandizing and media rights were an $892 million business last year, Schacther suggested. For perspective, that's less than the $970 million that Amazon paid for Twitch. By 2020, Macquarie expects e-Sports revenues to quintuple, hitting $5 billion.

That is still a small number for Amazon, with $165 billion in projected 2017 revenue and a $400 billion market cap, or Google parent Alphabet, which has a projected $87 billion revenue and a $578 billion market value.

While the dollars are modest in Silicon Valley terms, e-sports can attract tens of millions of young eyeballs around the world and represents an attractive demographic.

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Editors' pick: Originally published March 22.

The final contest of the 2015 League of Legends gaming championships drew 36 million online viewers, topping the 31 million who watched Lebron James lead the Cleveland Cavaliers beat the Golden State Warriors in the last game of the NBA finals last year. The numbers are relative, of course. The gamers on the Koo Tigers and SK Telecom squads don't attract advertising dollars in quite the way that LeBron James and Stephen Curry do. 

Gamers' numbers do count, though. More than 35,000 made their way to San Diego for TwitchCon 2016, Amazon Game Studios announced three new games at the three-day event. Late fall Amazon also announced a new slate of gaming benefits for users of its Prime service.

"Twitch helped drive [Amazon]'s ~$1bn+ in display ad revenue last year," Macquarie's Schachter wrote. "Additionally, Google is ramping up on YouTube Gaming to capitalize on eSports' growing grassroots community of streaming gamers and fans."

Facebook has gotten into the game, although later than Amazon and Google. Last year, Facebook notched a streaming deal with Activision

While Twitch and YouTube Gaming may be the top seeds, Facebook and others can still fight their way onto the e-sports bracket. 

"Whether Twitch, YouTube or someone else becomes the dominant eSports streaming site is debatable, but the bottom line is that eSports streaming is growing, and judging by the industry dynamic in China, where there are multiple large streaming sites, we think the market is big enough for both [Amazon] and [Google], as well as broader mainstream media adoption," Schachter wrote.

While comparably smaller than traditional sports broadcasting, game streaming has one advantage. The Super Bowl and March Madness come just once a year. For the Twitch and YouTube Gaming demo, every day after school is game day.