'The pictures speak for themselves' - Jurgen Klopp reacts after Andy Robertson 'elbow' controversy with assistant referee Constantine Hatzidakis

• Robertson clashed with Constantine Hatzidakis at half time
• Official appeared to swing an arm at Reds defender
• PGMOL are investigating incident

WHAT HAPPENED? A pulsating 2-2 draw at Anfield featured a remarkable incident as, after referee Paul Tierney had blown for full time, one of his assistants, Constantine Hatzidakis, seemed to swing an arm towards Robertson as he looked to approach the official. Robertson reacted angrily, and was booked by Tierney for his protests.

WHAT THEY SAID: Speaking in his post-match press conference, Klopp said he had not seen the incident but that he had spoken to staff and players. "I didn’t see it," he said. "Now obviously I have time to watch it but I didn’t, just because I cannot give you the answers. I didn’t see it. I heard the pictures speak for themselves. I cannot say anymore. I didn’t see a bit."

Asked if either Tierney or Hatzidakis had approached either him or Robertson to explain, Klopp added: "No. They don’t come to us. If we have something we have to go to them, and I didn't want anything. I think there are some things we can talk about but they are not really helpful, but we had our issues with some referees."

THE BIGGER PICTURE: The Professional Game Match Officials Limited (PGMOL) issued a statement on Sunday evening saying they would investigate the incident.

It read: "PGMOL is aware of an incident involving assistant referee Constantine Hatzidakis and Liverpool defender Andrew Robertson at half-time during the Liverpool v Arsenal fixture at Anfield. We will review the matter in full.”

IN THREE PHOTOS:

WHAT NEXT? If found guilty, Hatzidakis could face a hefty ban from officiating. Fulham striker Aleksandar Mitrovic recently received an eight-game ban for laying hands on referee Chris Kavanagh during his side's FA Cup defeat to Manchester United, but there are few precedents when it comes to match officials doing something similar to players.