Arsenal were down to 10 men inside the first 20 minutes of their showdown against Chelsea at the Emirates Stadium this afternoon.
Per Mertesacker, who became the fourth different Arsenal player to be sent off in their last five league meetings against the Blues, was handed his marching orders after bringing down Diego Costa outside the area.
Chelsea broke forward after an Arsenal attack came to nothing with 18 minutes on the clock, and when Willian's through-ball found Costa, Mertesacker tried to nick the ball from the Spanish international only to take the man instead.
The home fans were further enraged when Arsene Wenger opted to take off striker Olivier Giroud, who was reportedly carrying a knock going into the game, in order to reinforce his backline with Gabriel. To add insult to injury, Costa was the man to put the ball in the back of the net just minutes later to give Chelsea a 1-0 lead.
The sequence of events sent Arsenal into overdrive on Twitter, and you can check out the best of the response below.
There's still plenty for the Gunners to play for this afternoon as they look to return to the top of the table. With Manchester City dropping points against West Ham yesterday, and Manchester United losing against Southampton, Wenger will be desperate for his side to fight their way back into the game and grab at least a point.
For Chelsea, the opening half couldn't have gone better if they'd planned it, with Costa bagging his fifth goal in as many league appearances.
The biggest concern for Blues boss Guus Hiddink will be the fact that the temperamental forward is once more going head to head with Gabriel, having received a ban for an altercation with the defender when they last met.