If you visited ESPN.com Sunday afternoon, there was a newcomer to the front page. The International 4 — the annual world championships of the mega-popular videogame Dota 2 — are taking place at a sold-out KeyArena in Seattle, and ESPN is helping to bring eSports into the mainstream by broadcasting the final rounds on ESPN 3.

It’s looking more and more likely that the next big sport in America is virtual. More than 300,000 people are watching The International on video game streaming site Twitch, the fourth-leading website in peak internet traffic in the United States, and professional Dota 2 and League of Legends games regularly attract hundreds of thousands of viewers every week from across the globe. Dota 2 has more than 7 million monthly players, while League of Legends has more than 67 million users worldwide. The League of Legends season three world championship was watched by more people than the NBA Finals, World Series and BCS national championship.

Dota 2 and League of Legends are MOBAs, or multiplayer online battle arena games. In very simple terms, teams of five players pick characters from a diverse roster and try to destroy the other team’s base on a battleground (while protecting their own). The games are incredibly complex and strategy-oriented, making them somewhat difficult to get into for new users, but each has built up a ridiculously large following.

Both Dota 2 and League of Legends have a number of professional players that make a living off of playing the game competitively and streaming to millions of followers on sites like Twitch. The team that wins The International 4 will take home more than $5 million in prize money, which is four times what Rory McIlroy earned by winning the British Open ($1.6 million). ESPN also televised a Call of Duty tournament that was part of the X Games earlier this summer. It’s not unfathomable to think that in a few years, Dota and League of Legends highlights might be a regular part of SportsCenter.