Has Gil ever played high energy, quick, pressing football before? I'm pretty sure that Elche and Valencia don't play that way so I can see why he isn't playing at the moment. We only have to look at Sanchez to see that our other player coming in from La Liga wants too much time on the ball and it might just be that Gil isn't quite ready to press and play as quickly as Sherwood would like.
Also I would add, in a relegation dogfight who are you going to rely on to start most games, experienced premier league players or an untested kid from Spain? If there is one place available to try out a youngster as well it deserves to be one of our youth products, especially when they have as much potential as Grealish, so he is probably just a victim of circumstance.
Nothing to see here imo.