Way back in 2014 we wrote about the growth of e-sports, and how it was already a billion-dollar business. In the years since, it has only continued to grow… which explains why a streaming outfit founded by Major League Baseball would be spending more than $300 million to bring live-streaming game competitions to the masses.

League of Legends is far from the only game on the highly-competitive e-sports scene, but it is probably the biggest. Developer Riot Games recently admitted the title is pulling in more than 100 million unique players per month, worldwide.

The prize pool for victors in the 2016 World Championship, held in October, was more than $5 million. At its height, the tournament drew 14.7 million concurrent viewers. Overall, 43 million viewers livestreamed a total 370 million hours of play — and that doesn’t even include the 15,000 fans who attended the Los Angeles finale in-person.

For comparison, game 7 of this year’s landmark World Series between the Cleveland Indians and Chicago Cubs — the most-watched baseball game in 25 years — drew about 40 million viewers.

Where there are that many viewers, there is clearly money to be made. And that’s where today’s deal comes in.

Riot Games is signing an agreement with BAMTech — Major League Baseball’s streaming tech division — to broadcast League of Legends competitions.

BAMTech will be paying at least $300 million for the exclusive rights, the Wall Street Journal reports, with the plan of launching a dedicated streaming app for phones, PCs, and other devices in 2017. Content will also be available on other platforms, like Twitch.

The partnership with BAMTech will allow Riot Games to “grow revenue in our sport through various means, including sponsorship and advertising,” Riot says in its press release. In short, internet-broadcast competitive video game championships will work a lot like traditional or streaming broadcasts of the kind of sports you play with a ball or a puck.

Disney dropped a cool $1 billion on BAMTech back in August, with the goal of using it to offer a standalone ESPN-free ESPN streaming service.

At the time, BAMTech already had licenses to show MLB, NHL, and some college sports games. Now, it’s pulling in the digital side, too.

The WSJ estimates that e-sports will make up 10% of all U.S. sports viewing by 2020 — well under five years from now.

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