Placement Matches

Has anyone figured out if there's any rhyme or reason to them?

I ended last season at Silver 4, and my buddy ended at Gold 5. We played all 10 placement matches together, and went 7-3.

I got placed in Silver 4, and he got placed in Gold 3.

How did this happen? My KDA was 3.9 and his was somewhere around the same. We played exactly the same matches, and most of them were against previous mid-Golds.

How did HE go up and I go NOWHERE, despite the fact that I was beating people out of my ELO and he was beating people BELOW his?

I am legitimately curious- not really whining.