Referee Neil Swarbrick appeared to send off the wrong player in the second minute of Manchester City's 3-0 Premier League win against West Brom.
Defender Craig Dawson fouled Wilfried Bony on the edge of the area, but Gareth McAuley was shown the red card.
West Brom manager Tony Pulis spoke with Swarbrick at half-time.
Pulis, who was clearly frustrated with the official's decision, waited until Swarbrick had left the pitch but continued to speak as they disappeared into the dressing room area.
BT Sport's Darren Fletcher said on commentary during the match that the referee told a BT Sport reporter at half-time that it was a case of mistaken identity.
Fletcher added that the first number the official saw during the incident was McAuley's 23, rather than the 25 of Dawson.
BBC Radio 5 live pundit Danny Mills called it a "ridiculous decision".
"We need to hear from the officials, because I don't understand what was going through the referee's mind," he said.
"I'm sorry but that is just a horrendous decision. One player has got Dawson on his back, and the other has McAuley.
"Does the referee not have the common sense to just say to one of his officials, have I got the right man? They are all mic'd up."
Brown was sent off by referee Roger East in his side's 2-0 defeat against the Red Devils, despite television pictures showing that John O'Shea had fouled United striker Radamel Falcao.
The FA upheld a claim of wrongful dismissal and neither Brown nor O'Shea had to serve a suspension.