Suggestion: You can not play a champ in ranked without X-Mastery in that champ
So I have had a string of games lately (not just Yuumi) but in general, where I am in a Gold 1 ranked game or going for my Plat promos, then on the load screen I see that my teammates are playing champs that they have 0 mastery on. I am all for trying new champs and having fun, but it is BS that someone can play a champ that they have NEVER played in a game vs others with in ranked.
I think there should be a floor of the required mastery to play a champ in solo ranked queue. Even if it was like 10,000 or 5,000 - get a few games under your belt before you come into ranked with it.
It makes for a fun promo when your top Sylas has 0 mastery and goes 1-13. This has been happening more and more lately and its frustrating for people with zero experience on a champ to tank a game. I am aware that they could have put in countless hours on the practice tool or PBE server on a champ. Then it should be no problem for them to do a few normals to get the required mastery level to play the champ in ranked.