Chelsea had a high amount of possession during the first half, but without being able to create many chances. Cardiff would defend deep and wait to counter on the wings, where they would win set pieces to provide a platform for creating chances.
With the ball, Chelsea had to play most of their game from the back through Rüdiger. Niasse would stay closer to David Luiz and Camarasa marked Jorginho — leaving time and space on the ball for Rüdiger to carry forward. When carrying the ball forward into space, he would eventually draw pressure from one of Cardiff’s central midfielders (which would allow one of Chelsea’s central midfielders to pull off the back of them to find space), but Chelsea only found the free man on a few occasions from here, most notably the first-time pass made by Jorginho for Higuaîn inside the box.
By taking David Luiz out of the game, Cardiff took away Chelsea’s main forward passer from the back, reducing the amount of long passes behind their defence, and restricting Chelsea to wing-to-wing passing without any penetration to get behind.
The best opportunities to break down Cardiff came when Rüdiger was able to find Willian and Pedro moving inside between lines, which resulted in Pedro coming close with a shot from outside the box.
When Cardiff had the ball, they were much more dangerous than Chelsea. Niasse would run behind on the wings, and both wingers were able to carry the ball forward and take on defenders. By advancing up the wings, Cardiff could use the space left behind Chelsea’s fullbacks, draw Chelsea’s central defenders out wide, and win set pieces. The latter is their main attacking threat as a team — they can create good opportunities from corners, free kicks and long throw-ins by directly playing into the box, sustaining attacks, or drawing further fouls in and around the box.
Sooner or later Cardiff’s set pieces would provide them with a chance, and early on in the second half they took full advantage to take the lead. Following this, the game opened up, with Cardiff having the ball a little more and Chelsea being able to counter and attack with spaces — Willian using his individual talent to create shooting opportunities for himself and others.
In an open game where individual talent could shine, Chelsea chose to introduce their most talented attacking player early in the half, giving him more time on the field to change the game, and he immediately caused Cardiff problems by winning a free kick on the edge of the box.
Rather than the wingers remaining wide and having Rüdiger carrying the ball forward into space like in the first half, Hazard would instead drop to collect the ball and carry it forward to advance into the final third.
Since Hazard was now taking the ball forward from central midfield, the second change was needed to alter the roles of the central midfielders. Loftus-Cheek offered more of an offensive threat inside the box, while Kovacic could use his mobility to cover better defensively and not risk Jorginho defending large spaces on a yellow card.
The final change came down to the choice of bringing on Hudson-Odoi and switching to a 4-2-3-1 (as Chelsea have done in previous games) or bringing on Giroud to offer an option for crosses and set pieces. Sarri opted for the latter, and Giroud’s presence in the box would go on to indeed cause Cardiff more problems than Higuain.
Chelsea were able to create chances by overloading Hazard and Willian on the same wing, and ensuring that there were multiple strong options to aim for in the air (much more than they’ve normally had in other matches this season), such as Giroud, Alonso (flick-on assist for the equalizer), and Loftus-Cheek for the winning goal.
xG map for Cardiff - Chelsea— Caley Graphics (@Caley_graphics) March 31, 2019
Cardiff got a goal out of nothing and attacked poorly all match. Chelsea needed some favor in the refereeing to get the points back. pic.twitter.com/hBvABxgrHZ
Cardiff’s set up in the first half, allowing Rüdiger time and space on the ball, rather than Jorginho or David Luiz, restricted Chelsea to few opportunities with the ball form open play. Meanwhile, Cardiff were able to cause problems by countering on the wings and winning set pieces in the final third. After going behind early in the second half, Chelsea brought on Hazard with freedom to collect the ball from defenders and take it forward to create chances in the final third. Chelsea’s final changes brought a better offensive and defensive balance in midfield, and increased their threat in the air from crosses and set pieces, to come back and win the game late on.