Normals Matchmaking

I really need someone to explain matchmaking to me. For the past few weeks, I've been getting placed against Diamond players in normals. I'm gold 5. I've been told that normal mmr and ranked mmr are independent of each other, but then there still seems to be an issue if I'm matched against someone who had the skill to make it to diamond, when I'm still only gold. This has made my last few games rather unplayable. Thanks to anyone who can help.