I wouldn't know how to be honest. You can try to pick holes in it, playing a sweeper, putting someone permanently infront of the back four but there's so much strength, clever movement and depth with them, you can't pick out single players or parts of the system and hope that by stopping that you stop them, it doesn't work like that, it can't work like that because they tend to walk all over practically everyone. I don't think you can open up against them, I think that's suicide, the best bet I suppose would be to compress the space around the back four to limit the movement and space for them to play into, despite their ability to play the ball through the eye of a needle. Pepe would actually be a good keeper against them as he's a sound sweeper, that negates the need for you to employ and third centre half who gets everything that drops in behind. A keeper that's quick off his line and a defensive midfieder or two infront, creating a diamond formation at the back, and two full backs who tuck in to create a narrow back four. They have the ability to get in behind which then becomes a worry, but in the percentage game they're more threatening through the centre and getting in behind with a through pass, rather than going around the defense with an orphodox wide player. Either way though, it's a tough call. They scored last night through Silva with a bit of wide play.
And that's just about them. How do you keep the ball long enough to be a threat regularly enough to get enough goals to put the pressure on them? You simply don't. I do think they've got vulnerabilities at the back but it's holding possession long enough to exploit those weaknesses. They keep the ball to take the pressure off and their best form of defense is attack. As said, you have to get at them quickly and make sure what chances you do get you take, which is a big ask.