Manchester City struck a damaging early blow in the Premier League title race as they stormed to a 3-0 victory over a below-par Chelsea on Sunday.
Following a turbulent week in which a dispute between Chelsea manager Jose Mourinho and his medical staff dominated the headlines, a win at the Etihad Stadium would have been just what the doctor ordered for the reigning champions.
However, with doctor Eva Carneiro and physio Jon Fearn absent from the Chelsea bench, Mourinho's men were unable to restore confidence in their ability to defend the title they won so convincingly last term.
City dominated throughout, but Sergio Aguero found Chelsea goalkeeper Asmir Begovic in inspired form during the opening period and was denied time and again as he threatened to break the deadlock.
Aguero eventually found a way past the Bosnia-Herzegovina international shortly after the half-hour mark, having created space for himself in the Chelsea box.
Vincent Kompany doubled the lead with his second goal in as many matches in the 79th minute, before Fernandinho made absolutely certain of a fully merited three points with a fierce drive six minutes later.
Begovic came into the Chelsea starting XI for the suspended Thibaut Courtois as one of two changes to the side that drew 2-2 with Swansea City last weekend, and the former Stoke City stopper was called into action inside the opening minute when Aguero - in for Wilfried Bony as City's only alteration - was sent clean through on goal by David Silva.
The Argentinian failed to find a way past Begovic and Jesus Navas drilled wide from the rebound.
Begovic was making a promising start to his full Chelsea debut and got down brilliantly to his left to keep out another Aguero strike on 16 minutes, before pulling off an almost identical save from the same man a minute later.
As encouraged as Mourinho will have been by the early performance of his stand-in keeper, the fact he saw as much action as he did in the opening 20 minutes will have given the Chelsea boss some cause for concern.
And the Portuguese's worst fears were realised in the 31st minute, when Aguero and Yaya Toure exchanged passes on the edge of the box - the former tying Gary Cahill up in knots and guiding a low effort beyond Begovic into the bottom left-hand corner.
Cesc Fabregas - making his 50th Chelsea appearance - fired just wide as the visitors chased an equaliser and, after making such a positive start, Begovic found himself responsible for giving Cahill a bloodied nose as he attempted to punch clear an Aleksandar Kolarov free-kick in the 44th minute.
The first appearance of Chelsea's medical staff on the pitch prompted a chorus of ironic cheers and chants of "Eva, Eva, Eva" from the home fans.
Tempers flared as the players left the pitch for half-time, with Diego Costa feeling aggrieved after being caught by the flailing arm of Fernandinho.
Mourinho replaced John Terry with Kurt Zouma for the second half - the first time he has substituted his captain in the Premier League - and Ramires thought he had pulled Chelsea level five minutes in, but the linesman raised his flag for a marginal offside as the Brazilian obliviously wheeled off in celebration.
Chelsea pressed higher up in the second period and could have restored parity after 70 minutes when the ball found its way to the feet of Eden Hazard in the box following a counter-attack, but the Belgian fired straight at goalkeeper Joe Hart.
The visitors then fell further behind as Kompany outmuscled Branislav Ivanovic to double City's advantage with a goal similar to the one he scored at West Brom on Monday.
And the rout was complete five minutes from time - Fernandinho rifling home from the edge of the area as Chelsea's defenders switched off.
Costa hit the post in stoppage time, but even a goal would have done nothing to spoil City's day.
