This is a glitch and I don’t know how to fix it
You can only have up to 4 rares, you’ll need to fill 4 slots with commons or epics.
EDIT: That looks to be not true any longer. Did you try to reset the game recently? I was able to field 8 rares as a team.
Have you tried turning it off and back on again!!
Gotta love the classics.
I mean… sometimes that’s the answer.
Problem resolved thanks