Arsene Wenger claimed Chelsea's opening goal was a clear foul after his Arsenal side were beaten 3-1 at Stamford Bridge by the Premier League leaders.
Marcos Alonso opened the scoring when he climbed above Hector Bellerin to head home a rebound, but the Arsenal defender soon left the pitch injured after being caught by an elbow in the incident.
'The first goal was 100 percent a foul,' Wenger said.
Eden Hazard doubled the lead with a wonderful solo goal early in the second half before former Gunners captain Cesc Fabregas finished them off with five minutes to go, lobbing home after a mistake from ex-Chelsea goalkeeper Petr Cech.