Ashley Cole may have sparked an incident in the tunnel as Roberto Mancini fumes over key decisions at Stamford Bridge.
Tensions run high as Chelsea defeat Manchester City
Although it seemed reasonably peaceful after the final whistle - Andre Villas-Boas and Mario Balotelli exchanged a friendly greeting - there was some underlying tension at the manner of Chelsea's victory.
And Mancini claimed some pushing and shoving had been triggered by Cole, something later denied by Villas-Boas.
When asked what had happened, Mancini said: "I don't know if Cole said something.
"I don't know what he said. I don't understand."
Of more concern to the City boss were a succession of decisions he felt had gone against his side, leading to their first Premier League defeat of the season.
Balotelli put the visitors in front after less than two minutes.
However, referee Mark Clattenburg missed what appeared to be a clear foul in the penalty area on David Silva by Jose Bosingwa.
He then sent off Gael Clichy - City's third red card in six Premier League games - before awarding the home side a spot-kick eight minutes from time when Daniel Sturridge's piledriver struck Joleon Lescott on the arm.
"I agree with all of his decisions," said Mancini, with more than a hint of sarcasm.
"There was a big penalty. There wasn't a fan inside the stadium who didn't see it.
"But the referee was very close and he didn't.
"I don't know (about Chelsea's penalty).
"The Chelsea player shot very hard from five or six metres. It is difficult for the defender.
"But, at that moment, the referee was really sure.
"It was after the sending-off, that the game totally changed."
Villas-Boas said: "We've been having our decisions that have not been going our way and today it maybe didn't go Man City's way.
"But that's the nature of the game and at least our penalty's a blatant penalty."