Liverpool left-back Andy Robertson was struck on the face by assistant referee Constantine Hatzidakis in a remarkable incident just after the half-time whistle of Sunday's Premier League clash with Arsenal.
The Scotland captain approached the linesman, who then thrust his elbow into Robertson's chin.
Robertson was then shown a yellow card by referee Paul Tierney as he furiously protested.
Arsenal led 2-1 at half-time as the Gunners aim to take a step closer to the Premier League title.
