Matt Bloxham on why Simic isn't getting game time for the first team yet:

"He is adjusting to the British game and is working really hard on that. His movement has been first class and his goal return has been first class. But we are looking to prepare him for the physical robustness that the first team would require in the Championship."

That might mean that they want him to do more fitness work and/or bulk up a bit first, and that's fine. But I don't think playing against youth team defenders is going to prepare him in any way shape or form for your average Championship centre half. At some point, they have to give him that experience; maybe he'd have been better served going on loan to, say, Scotland?

As for the drop-off of the 21s, probably more difficult to explain. IIRC, Riza was saying a few of them spend more time with the senior squad, so that probably hasn't helped in terms of continuity. It must be difficult for those players to stay motivated too, in fairness. Take Luey Giles, for example. On Friday he was playing against Marcos Asensio and Ollie Watkins in front of 40,000 people. Yesterday he was playing against some teenagers in an empty park. I'd probably struggle to get myself up for it as well.