For me the most significant factor was the change to a 4 at the back. We look almost clueless at times in that system characterised by a lack of options on the the ball and a lack of fluidity. Having holgate makes a absolutely huge difference because let's be honest williams is absolute woeful on the ball and Mori is only marginally better. Not to mention the players further up the field also benefit. Lookman is not a winger and looks far more dangerous in a more central role which 3 at the back provides. And finally. Lukaku is incredibly isolated when we play the system we did yesterday. Not sure why Ronald has changed it tbh. Even against Bournemouth it was crying out for it second half and that is when we took control of the game, after holgate came on. One poor half against Stoke and it seems Koeman has for some reason holding that against Mason