Borussia Dortmund met Chelsea with 4-5-1 in set defences. Wingers came to midfield line.
Chelsea had 2 centre midfielders and 3 forwards. All forward players had enough ability to take position between forward and midfield lines so because of that, Borussia Dortmund stoppers needed centre midfielders to come closer to defense line and help them. Because Dortmund defense line didn’t try to push back Chelsea forwards with taking position as possible as closer to their own midfield line.
The problems were, first of all, centre midfielders shifted wings too much. This time when Chelsea passed the ball to more central spaces, centre was free and only other wing’s winger was able to take position in centre. Especially in crossing position, Chelsea could benefit from Dortmund’s this weakness.
Bellingham supported forward too much. So because of that a lot of times, Borussia Dortmund had to defend centre midfield with 2 centre midfielders instead of 3.
This is how Chelsea scored their first goal. Salih Özcan, Emre Can and Bellingham were Borussia Dortmund’s centre midfielders for this match. In this position, Salih Özcan is in the wing, Bellingham is not in centre and not close enough to midfield (because he was pressing to Chelsea defenders a few seconds before so he could not able to come back to midfield) and Emre Can takes position between 2 stoppers. So only Marco Reus was able to cover defense line’s central front and there were a lot of Chelsea players in Dortmund’s defense line’s front.