A Sergio Aguero hat-trick, Raheem Sterling’s double and an Ilkay Gundogan strike handed the Blues one of their worst defeats in Premier League history.
City led 2-0 after just 13 minutes, and had looked in control of proceedings at the Etihad as they look to pile pressure on title rivals Liverpool.
But midfielder Barkley, handed a rare start by Blues boss Maurizio Sarri, didn’t make matters any better just six minutes later.
Having seen David Luiz head the ball clear of the box, the England international bizarrely decided to nod it back towards his own goal, as opposed to hoofing it away from the danger.
“Ross Barkley is still an evertonian”
But the ex-Everton man’s attempts backfired, as his header fell short of Blues stopper Kepa and straight into the path of Sergio Aguero, who gladly slotted home to make it 3-0.
However, some viewers refused to believe it was an honest mistake from Barkley, picking up on his past allegiances to Liverpool’s bitter rivals.
Taking to Twitter, fans didn’t take long to share their conspiracy theories.
One wrote: “Ross Barkley is still an evertonian helping #MCFC like that.”
“The evertonian coming out in Ross Barkley there hahaha,” another joked.
And a third added: “Ross Barkley’s inner Ev coming out there.”
Understandably, Chelsea fans weren’t best pleased with their player either.
“Barkley is so braindead, useless player,” one angrily tweeted.
“I wonder what Ross Barkley does in training to get selected each and every week,” another added.