Q: How do you even speedrun rocket league? A: There is a season mode in the game against AI opponents, which can act as this game's "story mode" in a sense.
Q: Okay.. but every match has a strict five minute time limit, how do you even save any time? A: To save time in this game, you have to cut out as many replays and overtime battles as possible. You want to win enough matches to beat season mode, and make as many games end with a score of 1-0 as you can. You also want to keep the ball from being in the air for too long when the timer hits 0.
Q: Any additional tips? A: If you position yourself in various places near the opponent's goal with the ball, rookie AI will often be too concerned about defending the goal than going after the ball, so you can just stall for time. Also shoutouts to Braininator for this strat: If you wait until the clock has 0 seconds left on it before the first goal of the game is scored, you can avoid having to wait for the ball to be reset even once during the game.