Referee Chris Kavanagh said he "didn't like" the decision to send off Declan Rice in Arsenal's draw with Brighton last month, but said he "had no choice".
Rice was sent off during the 1-1 draw at the Emirates Stadium for a second yellow card after nudging the ball away from Joel Veltman as he prepared to take a free-kick.
Arsenal manager Mikel Arteta said he was "amazed, amazed, amazed" at the decision immediately after the match.
Audio released on Tuesday night from the Premier League's latest episode of Mic'd Up revealed Kavanagh said he had no choice but to show the England midfielder a second booking.