For the next few days, Psyonix is testing Rocket League's upcoming Tournaments mode—which is releasing in full in the Spring Update—and you can join the brackets now to test it out.
To join in, right click on Rocket League in your Steam library, navigate to the Betas tab, and opt into 'tounramentsbeta.' An update will automatically download, and the next time you launch the game the Tournaments menu will be there for you. Note that you'll have to opt back out of the beta if you want to keep playing ranked games.
I gave it a go, placing second in a 1v1 Snow Day tournament, and it certainly upped the pressure on me—at least until I was embarrassingly down 11-2 in the final match, at which point it didn't really matter what I did. But hey, second!
The interface works as promised, though it took quite a while to join the first matchup after the start of the tournament, so don't quit out even if it seems to have stalled. You can also create your own tournaments, including private tourneys, with any mutators you like.
What's missing? The two main things on my wish list are the ability to chat with participants while waiting for a tourney to begin, and the option to spectate the rest of a tournament if you lose before the final round. The latter is crucial (and if the option does exist, I haven't found it) because private tourneys with friends aren't going to be much fun if we can't all watch the final (streaming can be a stopgap for now).
All in all, the interface is nice and I haven't had any major problems—except for that it's already in style to call your tournament 'Soccar standard' while actually putting the most absurd mutators you can think of in place. I ended up playing one game with a giant basketball in low-g with hyper-fast boost, which isn't as fun as it sounds.
Check out Psyonix's blog post for the full details and known issues.