I still think the crux of the issue is Robertson and Trent. Not that either are bad players, though the form of both has slipped alarmingly.
I think Robbo has declined a bit in recent seasons, he's no longer putting in the quality from wide that he once did. This is pretty much an energy thing, like he can still get up there but putting in that level of quality is just too much, having made the run. He's not the attacker he was, but is still a good defender. But he's been trying to adjust to not having Mane infront of him. Diaz is no slouch and gets stuck in, but he does that from a more advanced position, Mane would cover back quite alot into the left back position to help Robbo, and they would overlap at ease with each other.
Trent has never been a great defender, but had a good understanding between Salah and Henderson. Hendo is injured and/or ageing, Salah's role has diminished and changed somewhat, and as has Trent's. I feel like Klopp has pushed it and pushed it with the highline. He's expected more and more in terms of how high up the pitch we push to compress the play and how advanced Trent plays. I don't think it's all laziness, I think the more advanced Trent has got, the less defensively inclined he's been.
Teams are just looking at our highline and seeing it as easy fodder, because it is. Just put a ball into the space on the flank, or bypass the midfield with a well timed pass to a well timed run and you're in. Once we played the offside trap to perfection, with the best sweeper keeper in the business mopping up. Now the timing isn't there so much. Players are switching off, teams are getting better at breaking the trap and so on.
Klopp has to have a rethink. I admire that he persists with his systems in the knowledge that eventually it will work again, but the issue is when the personnel aren't there to execute it well. When you're team isn't quite functioning in tandem, it all falls apart. We've always been the sum of our parts, rather than a team who relies solely on excellent players and match winning individuals. Our success has been more mechanical, more team based than having the luxury of just buying the best players and knowing you'll always have someone who will pull something out of the bag. And that's where it's gone wrong. A few slips in performances, a high percentage of underperformers and the system falters with devastating effect. Not just slipping to narrow defeats, but looking like you're one step away from an absolute battering, as we got against United and Napoli. It's been coming. It's happened before when people haven't had their heads right. 5-0 v City, shipping 7 at Villa, the potential is always there for it to go horribly wrong. Sometimes we look/hope that precision will finally come back into effect, the motors will start up again and we'll find a way. I just don't see it at the minute. Even with some of our returning stars, there's a spark that's not there. Thanks in no small part to the decline of Henderson and VVD (as well as the aforementioned fullbacks issue), the departure of Mane and some pretty shoddy backing from FSG.
Klopp is a magnificent manager, but he's not so pragmatic as other greats have been. Even Pep. He has one way and he will persist with it even if the players aren't there. To me, Klopp would sooner write off a season and not disrupt his system in the hope of a longterm gain, than sacrifice his ethos for a quick fix. I expect this season to be very much one of transition, we just have to hope that we don't fall too far behind.