The Football Association (FA) has asked Jurgen Klopp to explain his comments about referee Kevin Friend following Liverpool's draw with West Ham.
The Premier League leaders went ahead at London Stadium on Monday through a Sadio Mane goal, with the officials failing to penalise James Milner for a clear offside in the build-up.
That decision in particular proved to be one of the match's big talking points, with many taking to Twitter to both mock and voice their displeasure with the decision.
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Klopp suggested Friend favoured the home side in 50-50 decisions after half-time, as the Reds went on to draw for the second game in a row thanks to Michail Antonio's equaliser.