Arsenal centre-back David Luiz was sent off just 25 minutes into the Premier League clash at Stamford Bridge.
With the score level at 0-0, Shkodran Mustafi’s weak backpass played Chelsea striker Tammy Abraham in on goal.
Abraham took the ball around Gunners goalkeeper Bernd Leno before Luiz brought him down.
The referee did not send see it as an honest attempt to win the ball and showed the Brazilian the red card.
The Blues were subsequently awarded a penalty, which was converted by Jorginho.