Not exactly sure why, but Kosov hasn't played the last 5 games (game 4 against Traktor, games 1-4 against CSKA).
My guess is that Kazan had someone injured who returned to the line-up and Kosov was the odd man out, which is a bit odd because I thought Kosov was one of their most noticeable players (in the good sense) in the games I've watched. I don't think he's hurt (unless he was injured at practice) since his TOI in the last game was on par with what he's played previously, around 10-13 minutes. I was hoping that Kazan would give him a bigger role than what he had with Magnitogorsk, but that doesn't seem to be the case so far which is a huge shame.