According to the developers, Rocket League wasn't their first physics-based video game involving cars and soccer balls in a cage. The first version, Supersonic Acrobatic Rocket-Powered Battle-Cars”, was released in 2008 for PS3. While SARP wasn't nearly as successful as Rocket League, it remains a critically-acclaimed title among fans of the game for its incredibly fun and unique gameplay.
Before releasing Rocket League last year, Psyonix bided their time by doing odd jobs and contract work to earn enough money to fund the sequel to their previous title. By the time the game was released on July 7, 2015, the game had been in development since 2013.