He's not a keyplayer. In fact with marchisio the team still is slightly better, yet less spectacular. Keyplayer means massive drop in teamperformance when not playing, so that not quite the case.
I'm a fan of Pogba, but i'm not putting on pink glasses. He has potential to be a "one of a decade" player, but he isnt there yet. And marchisio, a player who's quality you do not understand, is still ahead and lets wait untill Pogba actually is consistantly better.
What you do will lead to dissapointment. If Pogba is really that good allready, he should score vital goals or assists in the next two games. create goals versus kopenhagen and boss the midfield against the stabbers without assistance needed from vidal or pirlo or the closest wingback. THAT is a keyplayer.