Sheaf always looks super on the ball when I've seen him. Really good technically and has a super pass on him. I don't know about him as a centre back but I can see him being pretty good in that Xhaka/Arteta role.
I completely agree with getting the average players out the door and giving these guys a chance. Elneny should go too so that the likes of Niles, Willock and Sheaf can get some good game time in midfield.
Don't think Nelson can complain much, getting any game time as a 17 yr old is impressive, especially if it's followed up by a Cup semi final appearance against Chelsea. If he thinks he'll get a better run out elsewhere he's in for a nasty surprise.