User blog comment:Krauserlols/Is Riven a real Wind Master?/@comment-8050014-20131220145723

Riven has two ultimates, the latter of which is called Wind slash. I think maybe she is not as skilled as Yasuo at using the wind and it takes a lot of concentration or effort, or maybe she just wasnt trained as well (she is Noxian), therefore it has a longer cooldown