I think teams are closing him down very quickly for one. But I also think he looks more uncomfortable receiving the ball higher up the pitch and with his back to goal, which he's done more since James arrived and Kelly came back. I don't think he suits the diamond at all and often pulls it out of shape by coming too deep for the ball. That's his natural game - drop deep and receive the ball to start attacking moves off and that probably is his strength, combined with then arriving late to the edge of the box. While his desire to play the ball forward is admirable, his link play is too often first time and rushed. Think we might also be coaching the flair out of him unfortunately.
So overall I'd put it down to other teams having picked him out as a danger after his early season form, being asked to play in a position that doesn't play to his own strengths and then who knows what other factors might be. Bit of fatigue at adjusting to the level, maybe he's home sick, maybe he's had covid, maybe he's thinking too much about what he's been coached here e.g. not giving the silly fouls away and it's taking the edge off his game.
