The only qualifying criteria is that your team must be entirely composed of silver players. This can include Libertadores cards rated 65-74 and special cards like Team of the Week providing they fall within that ratings window.

Re: Libertadores Cards do not count as rares in the Icon SBC's Bronze&silver. +1 and this is a major bug. These cards take up rare slots in packs that EA sells and advertises as having guaranteed rares, and they are absolutely defective because they don't work as rares in the majority of icon SBCs.