How Competitive Skill Rating Works (Season 9)

Does losing the first placement match have any effect on the outcome of your rank? (Say you have pretty solidified mmr). When placing other accounts it seemed like if I lost the first one my mmr bracket would be bumped down the next game.

Also, Is there a negative effect to losing your first 5 games in a row during placements, and then winning the last 5 in a row? Will this make you relatively where you ended even with the long streaks?