West Brom started with a 3-5-2 shape that dropped to a 5-5-0 in midfield (front two dropping to the sides of the midfielders), which gave them flexibility in pressing from the middle (midfielders pushing up) where they could match Chelsea’s numbers building from the back and be ready to take advantage of loose balls—leaving their backline deep.
Chelsea gave away a number of loose balls from the base of their buildup and would have to recover with fouls (which would later result in Thiago Silva getting sent off for a second yellow), but when they were broke through the pressure they would find themselves receiving the ball with space ahead of West Brom’s back five (dropping back to their own box) to then advance into the final third and find themselves in a number of promising positions.
After Chelsea’s goal and the sending off, Chelsea opted to maintain the five at the back, while West Brom would switch to a 4-4-2 after Ivanović was forced off. Although Chelsea’s change was to maintain the same buildup and attack with one less in the middle of the frontline, it left them very flat at the back when defending and leaving players to be isolated or able to be played around on the wings. West Brom’s change in formation made them more suited to the game being less organised and to attack with fast combinations on the wings, but this was made after the initial Chelsea change.
An alternate change for Chelsea here could’ve been to sacrifice Alonso for the central defender (Christensen), moving Azpilicueta to left back and maintaining the extra man from the frontline to support the midfield two, leaving the team more flexible in decision-making and shifting to the sides when defending — but it would be moving away from the back three that has served them well so far under Tuchel.
Chelsea continued to build and created a number of good chances to build on their lead, from breaking pressure or counter-attacks, but a long ball finding a perfectly timed run would see West Brom equalise before going on to win the ball high up and take the lead immediate after, and just before half-time.
This was the first time that Chelsea came up against a difficult moment in a game with Tuchel — moments that they’ve struggled mentally to overcome in the past. Keeping the same formation took away potential for excuses.
West Brom's xG is obviously low for a team that scored 5 but (per Opta):— James Benge (@jamesbenge) April 3, 2021
- At 1.58 it's by far the highest any team has registered against Chelsea since Tuchel's appointment
- No other team's xG vs Tuchel's Chelsea has been higher than 1
- Atleti's xG over two legs: 1.35
Mount coming on only maintained the number of attackers on the pitch, so Kovačić pushed higher up on the left. But this left Jorginho very isolated during transitions and when defending deep — both Mount and Kovačić needed to create with the ball, leaving space behind them when the ball was lost. It would again be a case of the back-five becoming very flat when having to get back to defend deep (or being left as a three when the wing-backs were high up) and leaving a lot of space ahead of them with only Jorginho to cover (or for someone to push up aggressively from the backlinee), leaving the risk of spaces for runners to exploit.
Whenever West Brom won the ball high up or got behind on the wings, they would find themselves in situations where they had numbers to attack the box quickly and a lot of space to be found ahead of Chelsea’s dropping backline. This saw them score two goals in a row that looked like standard shooting practice — with the player inside the box having time and space to pick out the finish.
Mount’s goal gave Chelsea some hope and belief, with a strong and aggressive reaction to the restart following it, but without being able to take advantage of this momentum Chelsea still found themselves two goals down in the final minutes of the game, at which point West Brom would instead go on to extend their lead further and finish off the scoring.
Chelsea made mistakes in building during the first half, which saw them go a man down after taking the lead, while also not taking advantage of a number of promising attacks on either sides of the sending off. The change to maintain the back five gave Chelsea fewer options, and the injury of Pulisic really limited what they could then change in the second half. West Brom would go on to score two more early in the second half, when they could continue to win the ball high up and get behind on the wings. Chelsea’s goal gave them a brief moment of hope, but continuing to miss chances would see time run out.