So then what’s changed this season. It can’t omly be Can not running back.
The midfield unit is not playing as a unit yet. No matter who is in there. It does just take one of them to ignore instuctions and suddenly you have gaps that the other two are needing to run around trying to fix - thus creating more gaps themselves - as highlighted in the breakdown of the Sevilla goal. Its actually a good example of why I said Chamberlain is being signed as a CM, yet won't play there until January, if at all this season. His distances would be wrong, he would press at the wrong times, he wouldn't know the triggers thus would be reacting to his team mates rather than reading play.
The trio is quite fluid in that they can all do each others jobs off the ball - yet have clear roles when everyone is in position. But they are all free to press when the triggers are there to do so. They just tuck in for each other and recover quickly.
When you watch our midfield fail though - it's interesting to see what the players do as it highlights their strengths and weaknesses. Gini and Milner look to close up spaces. Henderson and Can get attracted to the ball. Henderson tracks runners best.
When Gini is trying to solve midfield problems he looks at closing up dangerous spaces and can switch off to runners causing him to react late (see Watford 2nd, Sevilla 2nd). This isn't a huge problem. It is almost impossible to both be aware of danger in terms of space and men simultaneously. You tend to be reading one and not the other. It's also likely it comes down to first instruction. If there is a problem protect the zone Henderson vacates.
When Henderson is trying to solve midfield problems he wants to run. Track any runners, if there is no pressure on the ball, do that. He doesn't like to hold his position. As a #6 this can be a problem. Then again coupled with Gini who will be spatially aware for him in midfield that can work. It just needs the 3rd CM to be more like Gini (e.g. Lallana/Milner) and look to get in beside him as quick as possible instead of getting drawn to the ball (Can). It also needs the wide forwards (Mane, Salah) to drop and pick up the runners behind Gini if he is tucking into Henderson's zone. This requires them to read the midfield shape and see when it's getting stretched to breaking point. Salah is doing this, Mane isn't. A good example is the Watford 2nd goal (Gini tucks into the #6 role, Doucoure runs off Mane, Gini reacts late) the Sevilla goal (Gini tucks in for Henderson, Mane hasn't dropped as deep as Salah thus Correa runs off the back of Gini into the space between Lovren & Moreno). Again I think it's tactical instruction. Mane is staying high as the wide striker, Firmino drops into midfield and Moreno is trusted to deal with two players. Harsh, but it really does look that way. Then again if Can gets back in shape, that never happens. So it was a momentary problem that escalated due to inaction.
When Can is trying to solve the problem he goes to the ball. Doesn't track runners and isn't spatially aware. He often (but only this season that I have noticed) decides to simply not bother doing anything. Will stand or walk back into position while the rest of the team is running around fighting fires.