In terms of eSports, Rocket League is an infant. Just over 6 months old, this game should barely be able to hold up it's head. In terms of the internet, online gaming, and eSports, however, it's getting ready for college.
Rocket League came out quietly in July 2015. The developers themselves said that they expected 10,000 or less to be playing at the time of launch. Rocket League's Humble Beginnings Let me take you back 7 years or so.