Chelsea faced an aggressive and intense Porto defence, with speed to attack from counters, quick combinations on the wings in the final third, and a number of dangerous set piece routines.
Porto opened up much more aggressively to press on their left. Otavio would push up on the inside to press Jorginho and continue going through to Christensen, with Zaidu and Pepe pushing up to cover James and Mount. On the right, Matheus moved up onto Kovačić, while Corona dropped back to cover Chilwell moving forward onto the last line.
However, after pressing high up, Porto would leave spaces ahead and behind their block for Chelsea to use when dropping back to midfield. Ahead of the block, Chelsea’s backline and midfielders could move the ball until they found the spare man, which would then open up the possibility to play forward and exploit the depth left behind Porto’s high backline.
Although many of the opportunities to play behind were either missed (pass overhit) or not attempted (run made but pass not made), Chelsea found a problem area for Porto when moving deeper. On their left, Porto had Zaidu moving up from left back to press James when high up, but when deeper there was a switchover with him picking up Mount instead, or getting caught between the two, while Otavio tucked inside on the left, leaving James in space and Chelsea able to overload in this corner.
As the half went on, Porto looked to find solutions to this area with Diaz dropping back on the left to cover James (all the way back on the wing) or dropping inside to allow Otavio to move back to cover James. However, dealing with the positioning of Chelsea’s attackers in this area, along with Mount using his quality to turn quickly on the last line to break behind opposition backlines, would make the difference in the first half, giving Chelsea the lead going into the break.
Porto’s change of shape (3-5-2) continued into the second half, with Otavio on the right of the central midfielders (Matheus left, Grujic deep), Corona continuing to cover the full line on the right and dropping back to make a back-fve when defending, and Diaz on the left.
Chelsea had to deal with more deep defending in the second half and had a difficult time against the speed and overloads of Porto’s attacks. With the midfielders and wide players free to move wide or inside to overload, they could find spaces around Chelsea’s midfield to receive the ball facing the backline, before looking to play passes behind for runners inside the box or long shots on goal. Porto’s threat and pressure on Chelsea’s goal from corners continued as well, and required a number of blocks and active goalkeeping by Mendy to stop the initial danger, and multiple chances from second balls. Although Porto didn’t find the goal they needed, they certainly will have the possibility to score in the return leg.
Chelsea’s changes made a strong impact in the game, with the switch to a 3-5-2 giving them Kanté to make runs from deep, a target man to play off in Giroud, and Pulisic capable of making runs behind. As Chelsea regained control of the game with the ball following the changes, the opportunity to look for the passes behind Porto’s backline reappeared as well, and in doing so Chilwell was able to capitalise upon a mistake to win the ball and finish calmly to give Chelsea a good lead going into the second leg.
xG map for Porto - Chelsea— Caley Graphics (@Caley_graphics) April 7, 2021
Porto did everything they needed to take the game to Chelsea except for the scoring part pic.twitter.com/Rb5k9btJlS
Porto showed a lot of strengths in their intensity both with and without the ball. They caused Chelsea problems from corners throughout the match, combined quickly on the wings to get behind Chelsea’s backline, and created opportunities for long shots that could yet trouble Chelsea in the second leg. After breaking Porto’s intensity and pressure, Chelsea found spaces to have time on the ball and look to exploit the depth behind Porto’s backline, while taking advantage of the changeover of defenders on Porto’s left to create opportunities. A strong lead to take into the second leg, but wherein Porto will have plenty of potential to cause problems.