Chelsea fell to their first defeat of the season against the reigning Premier League Champions Manchester City.
The Blues opted to use three midfielders in the starting lineup, with the formation proving effective in the second half of the victory against Tottenham.
However, they were unable to get out of their own half due to City's relentless attacks going forward from the get go, with the pressure finally paying off thanks to Gabriel Jesus' finish at the start of the second half.
The visitors began the game with a high press against the Blues defence, with Reece James able to prevent Jack Grealish from sending a dangerous ball into the box.
Captain Cesar Azpilicueta cleared a cross shortly after.
Although City were looking the sharper side in the opening few minutes, Chelsea were able to limit their opportunities through their solid backline.
Grealish and James once again enjoyed a good battle on the right, with the latter drawing the foul from the former Aston Villa man.
On 15 minutes, Kevin De Bruyne sent a dangerous ball into the box but it was cleared by the Blues who broke away, with Romelu Lukaku unable to get on the end of Timo Werner's ball.
The German was in amongst the action again but his effort was deflected behind for a corner, which was eventually cleared.
Antonio Rudiger and Bernardo Silva involved in a spot of playful pushing, with referee Michael Oliver soon having a word with the Blues man.
James appeared to be struggling with an injury and was replaced by Thiago Silva, with Azpilicueta moving from centre-back to right wing-back.
City threatened again and both sides played pinball on the edge of the box, with Rudiger having to blast it out for a throw to clear the danger.
Rodri saw a shot deflected behind for a corner as the away side continued to press the Chelsea defence.
De Bruyne sent a long range shot way over the bar, and Tuchel appeared to be frustrated on the touchline with his side's play so far in this game.
Jesus was the next player to have a chance, but his effort from inside the box was volleyed well off target.
The Blues slowly but surely attempted to attack the City box, but were unable to get any effective crosses into the danger area.
Overall, the first half was dominated by City and their press, with Chelsea failing to generate any chances on the break. Werner and Lukaku did fairly well to link up in the attack but did not receive sufficient service.
No changes were made by either side at the start of the second half.
Grealish had the first chance after the break, with his shot curling wide of Edouard Mendy's post.
Soon after, Werner made a great run down the right hand side for the Blues but had no support up top with him.
However, City were the first to take the lead. Joao Cancelo's shot falls to Gabriel Jesus, who then turns and his finish bobbles past Mendy into the back of the net for 1-0.
The visitor's pressing finally paid off and the Blues worked hard to find a quick response.
Mateo Kovacic send a great through ball to Werner, but the pass was slightly overhit and Ederson collected it.
Mendy was called into action as he made a fantastic save to deny Grealish from making it 2-0.
Tuchel saw the system wasn't working and decided to bring in Kai Havertz for N'Golo Kante. The formation switched back to the preferred 3-4-3.
Thiago Silva then made a great stop on the line to prevent Jesus from getting a second.
Chelsea think they have an equaliser as Lukaku tapped in Havertz's pass, but the former was deemed to be offside in the buildup.
Aymeric Laporte brought down Lukaku on the edge of the box and was subsequently booked. Marcos Alonso's free kick was deflected behind for a corner.
City continued to press for a second but were once again shut out by the Blues backline.
Kovacic was the next Chelsea player to have a chance, with Dias deflecting his effort behind for another corner.
The Blues' final change saw Ruben Loftus-Cheek enter the fray for Jorginho.
Despite a flurry of chances in response to the City goal, Chelsea were unable to test Ederson in the visiting goal.
Laporte had a fantastic chance to double his side's lead as he was unmarked in the box from a corner, but he sent it wide of the post.
Werner, once again, was working hard on the right hand side but was still yet to receive any support in the attack.
Mendy continued his solid game as he denied Grealish in a one on one, keeping his side firmly in the game as they entered the final few minutes.
As the latter stages of the match progressed, Chelsea continued to generate chances going forward, with the attack failing to utilise their strengths.
City withheld the home pressure and did well to hold onto the three points.
The Blues now sit in third in the table, with City moving up to second.