Citation de TotitotaSalut :)
C'est par rapport à ton ratio victoires/défaites en non classé. On va te filer un adversaire qui à relativement le même ratio que toi. Je ne sais pas si ça prend en compte ton rang en classé par contre. ça m'étonnerait fortement.

Matchmaking works as follows:

We use a formula to assess player skill. After every game, the formula looks at if you won or lost and uses your current rating, your opponent’s rating, and your rating history to generate your new rating. We call this rating MMR for short. In casual and at Legend rank, we pair players with similar MMRs. In Ranked below legend, we pair people with similar star ranks instead of similar MMRs. Your rating is the only input that the matchmaker receives. It doesn’t know what deck you’re playing, what deck you just played with or against, or anything else, except for your rating.

When you press ‘play’ you enter a queue for your chosen game mode. The matchmaker looks at your MMR and compares it to the MMR of everyone else in the queue. If it finds someone else with the same MMR as you, it pairs you into a game. If it doesn’t, it will wait a few seconds and look again. The second time, it doesn’t look just for someone with your MMR; it will also look for someone with an MMR that’s almost the same as yours. If it still doesn’t find a match, it waits another few seconds and looks again. The bound for what MMRs are considered a good match keep widening the longer you’re in the queue; this is to ensure that you don’t have to wait too long to play. Usually a match is found so quickly that the widening bounds never really matter. After the game, your rating is updated, and the process is repeated the next time you queue up.