Did you know that every player will slowly get to 6500 MMR over time? In a Developer Insight in November they shared that there is a small boost that should slowly move you there.

[bluepost] Developer Insights: Personal Rating in Hearthstone Battlegrounds

We’ve also added a very small progression adjustment to your rating after each game. This adjustment always has a positive value and depends on your current rating unless you reach 6500 rating or above. The lower your rating is, the larger the adjustment. Therefore, in theory, playing more games in Battlegrounds will give you a small advantage in terms of “boosting” your rating (if you are below 6500 rating). Bear in mind that this is true whether you win or lose; think of it as a consistent progression adjustment that gives you a small positive bump each time you play Battlegrounds.

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