Andy Robertson appeared to be on the end of an elbow from one of the match officials during Liverpool’s game with Arsenal.
Liverpool players fumed at the referee during the half-time break, with Jordan Henderson leading the protests as the two sides went down the tunnel. The Reds trailed 2-1 at the break.
Former Reds defender Jamie Carragher, who was working for Sky Sports at the game, was quick to pick up on one incident, tweeting: "Linesman elbow on Robertson!"