Enzo Maresca's first Premier League game in charge of Chelsea ended in a hard-fought 2-0 defeat to reigning champions Manchester City.
The Blues created chances and had penalty appeals turned down in either half - plus had a goal ruled out for offside - but the game was ultimately decided by Erling Haaland's neat finish on 18 minutes and a late strike from Mateo Kovacic.
Quartet return
Maresca made four changes to his starting line-up compared to the side which drew 1-1 with Inter Milan, with Moises Caicedo, Christopher Nkunku, Cole Palmer and Nicolas Jackson all promoted into the XI.
The Blues started in a more traditional-looking 4-2-3-1 formation, with Caicedo starting alongside Romeo Lavia in a deeper position and Enzo Fernandez central, Nkunku off the left and Palmer the right.
Chelsea enjoyed a good start to the game and Wesley Fofana - playing in his first Premier League match for 448 days - volleyed over from a corner inside the opening ten minutes.
Opening goal
But it was Man City who went ahead in the 18th minute when Jeremy Doku's pass from the left wing was toe-poked beyond Levi Colwill by Bernardo Silva and after controlling well, Haaland drove towards the six-yard box and dinked the ball over the diving Robert Sanchez. After a VAR check for offside, the goal was confirmed.
Chelsea created a number of dangerous openings as the half went on but the next goalscoring opportunity saw Sanchez produce a fine diving save to deny a long-range effort from Doku.
Moments later and the Blues went close to equalising when a slick move saw Palmer pick out Nkunku at the far post and his nod down to Jackson resulted in the striker laying the ball off to Fernandez. His powerful shot was heading towards goal before being blocked by the City defender.
Silva had a shot saved for City before Chelsea thought they had the equaliser just before half-time when Palmer's left-footed shot from outside the area was fumbled by Ederson and Jackson converted the rebound. However, the striker had strayed into an offside position and the goal was ruled out.
The first half concluded with the Blues having two penalty shouts waved away in quick succession when Fernandez twice went over in the box.
The second period was only six minutes old when Sanchez saved well from a 20-yard strike by Haaland, which the goalkeeper parried away from danger.
Agonisingly close
Pedro Neto came on for his debut just before the hour mark and almost scored immediately when a slick passing move saw Palmer slide the ball to Fernandez inside the penalty area and his low cross from the right would have been tapped in by Neto at the far post had it not been for a world-class bit of defending from Rico Lewis.
The Blues went agonisingly close again a minute later when Jackson acrobatically volleyed goalwards from close range, only for Ederson to produce a fine point-blank save.
Maresca introduced another two new signings when Marc Guiu and Kiernan Dewsbury-Hall came on as substitutes as the Blues continued their search for three points.
The Blues had another penalty appeal dismissed when the ball struck the arm of Kovacic but referee Taylor adjudged the former Blue was so close to the ball he couldn't get out of the way.
And it was Kovacic who was to score the game's second goal when he collected a clearance from Fofana, drove past Caicedo and curled a 25-yard shot in with the help of Sanchez's palm and the post.
Palmer and Fernandez both forced Ederson into routine stops late on but the Blues were unable to find a way back into the contest.
What is next
Focus now turns to Thursday night's UEFA Conference League Play-Off first leg tie with Servette.
The Swiss side travel to Stamford Bridge for the first of two matches between the clubs, with a place in the group stage up for grabs.
The Teams
Chelsea: Sanchez: Gusto, Fofana, Colwill, Cucurella (Veiga 80); Caicedo, Lavia (Dewsbury-Hall 67); Palmer, Fernandez (C), Nkunku (Neto 58); Jackson (Guiu 67)
Unused substitutes: Jorgensen, Tosin, Badiashile, Mudryk, Madueke
Booked: Caicedo 89
Man City: Ederson, Lewis, Akanji, Dias, Gvardiol, Kovacic, De Bruyne (C), Bernardo, Doku, Savinho (Foden 46), Haaland
Unused substitutes: Ortega Moreno, Walker, Stones, Ake, Grealish, Nunes, O'Reilly, McAtee
Goalscorer: Haaland 18, Kovacic 84
Booked: Haaland 66
Attendance: 39,818
Referee: Anthony Taylor