West Ham tried to meet Chelsea in mid-block. At least they didn’t want Chelsea to come closer to their own penalty box so always they tried to push back Chelsea. West Ham’s defense line tried to don’t get too closer to penalty box.
When they tried to do that, midfielders and forwards didn’t press Chelsea players. They gave time and space Chelsea players. It’s not that much dangerous if you don’t try to meet opponent in mid-block or your defense line wants to push back opponent’s players. Because you can cover spaces behind you easily if you don’t leave much space in your behind.
But if you want to meet your opponent in mid-block and your defense line wants to push back opponent’s players and if your midfielders and forwards give time and space to opponent’s players, this time it causes problems for defending team. Because first of all, now attacking team’s players can pass the ball to forward players easily. Because your players don’t press them. Also opponent’s players have enough space in your team’s defense line’s behind to escape so they can take the ball easily.
In West Ham, wing backs couldn’t keep up with other defenders about offside. It’s because when Chelsea’s one winger made a run to West Ham defense line’s behind, wing back followed Chelsea’s winger unnecessarily too much. It’s because when wing backs followed wingers, wing backs were in pitch’s edges. So they didn’t have enough angle to see all other defenders’ movements and pitch’s all central spaces. For example, sometimes stoppers also had this problem but they could deal with it easier because they were taking position more centrally. So they had a better angle to see all other defenders’ movements and had a better angle to see important and central spaces.
For example in this position, Mudryk tries to escape from West Ham wing back Coufal’s behind. And Coufal can’t focus on central spaces and other defenders’ positions much enough.