Can only speak to Chelsea but we've improved immensely this season by switching from a pure zonal scheme to a hybrid one - right now we man mark the most dangerous 3 or 4 opponents with our shorter players with the aim being to put them off, and station our taller players in high traffic areas (e.g. Tammy or Havertz is always on the front post, Zouma is right in the middle of the goal, etc). The results speak for themselves - we've gone from comically bad to the best team in the league on set plays (at both ends). Huge credit to Anthony Barry, the highly-rated coach we brought in from Wigan who has been focusing on this among other things.