http://www.pcgamer.com/rainbow-six-siege-overhauls-casual-matchmaking-and-adds-theme-park-map-to-ranked-play/

Ubisoft has overhauled Rainbow Six Siege's Casual matchmaking system ahead of the game's new season. For the last four months the game grouped players for Casual games based on their Ranked matchmaking rating (MMR) but Season 3 will introduce a separate MMR for Casual play. Ubisoft says it will provide "better quality matchmaking".

There's also changes to make the game friendlier to new players, who will now start with a lower MMR than before. "A lower starting point for beginners means that they will be able to increase their MMR in a pool of players with a comparable skill level. This lower MMR rating will be erased over time as they win more matches, eventually placing them where they truly belong based on their skill level," Ubisoft explained in a Reddit post yesterday.