Playing a champion for the first time in Ranked?

When i start up a game in ranked i check my teammates stats on lolnexus and i cringe when i see that my adc has only played tristana 1 time in normal's or ranked. So i just watch the game unravel and see my adc making mistakes like miss clicking W into the enemy team. Shouldnt there be a thing where you have to play 10 games with a champion in normal's before it lets you play that champion in ranked or at least having to play the champion against bots 5 times?