It's all about how close they get to Lukaku when they're "roaming" for me, in that case. If Barkley does what he often does when played off Lukaku away from home i.e. get sucked into midfield and dispossessed with ease by hard working opponents before letting the game pass him by completely and leaving Lukaku to take on an entire back 4 by himself with no support, we're in for 90 minutes of pain and wave after wave of attack and then a week of blaming Lukaku for it on here. I have no idea what Davies will be like in that position really. Having him there instead of Mirallas could help Barkley. Barkley definitely played better in his deeper role alongside Davies, so who knows.
It's really hard to know what'll happen here, but I can think of a few things that could go wrong that wouldn't surprise me.
