I do not understand why anybody would want Grealish anywhere near the starting 11 right now.
This is the toughest, most physical league in the world with biggest names running around the pitch. The team we support is Aston Villa (L6, D1 out of the last 7). Do you really think a teenager who has proved NOTHING yet is capable of somehow transforming the rot? We need experiance, and as much as I do not rate Nzogbia, I would pick him over Grealish any day of the week.
If we are winning (sound like an unlikely situation) and are controlling the game, then we can think about putting him on.