Sure, Barkley is ten times the player when he's on form and your post is perfectly reasonable, however, yours isn't the kind of view on the matter I was referring to.
Personally - and it's taken me a long time and a lot of excellent performances to get to this point - I'm starting to feel like it's difficult to leave the fella out of the side, even with players returning to fitness. He's a proven slotter now and offers much more to us than just that. Clubs are paying huge sums of money for what he does and often the players they're buying don't do it nearly as well. We can rely on him to score goals and I'd feel more confident of a goal, whether we're playing well or not, as long as he's on the field. He certainly doesn't hinder our build up play as the Burnley and Lille games have shown recently.