*So far*, Leverkusen and Liverpool have outpressed us. Chelsea might, but that's still unknown right now. I'd wager that, should we get that far in Europe (unlikely, but still), the real big dogs (Dortmund, Bayern, Barca, Madrid, Juve) will *selectively* press us enough to force us into errors similar to those we made against Leverkusen. That's not a fault of our system per se, just superior skill and experience coming up against our side.
Arsenal were caught in that half-space where they tried to selectively press us but weren't very good at it. Sanchez ran like a dog, but his team-mates really let him down on that score.