Liverpool: Liverpool captain Steven Gerrard issued a frank apology on Sunday after being sent off during his side`s 2-1 Premier League defeat at home to arch rivals Manchester United.
The 34-year-old, who will join the Los Angeles Galaxy at the end of the season, came on at half-time with Liverpool trailing 1-0, only to be sent off after 43 seconds for a crude stamp on United midfielder Ander Herrera.
"I don`t know what caused it. I don`t know. Probably just a reaction to the initial tackle," Gerrard told Sky Sports.
"I shouldn`t say more about it, really. I`ve just come out here to apologise to the dressing room and supporters.
"I need to accept it. The decision was right. I`ve let down my team-mates and the supporters. I take full responsibility.
"I`ve been in the game long enough (to know what happens) when you do something like that. I take full responsibility."
Juan Mata scored twice for United, with Daniel Sturridge replying for Liverpool, as Louis van Gaal`s side established a five-point lead over their rivals in the battle for Champions League qualification.
United striker Wayne Rooney also saw a stoppage-time penalty saved by Liverpool goalkeeper Simon Mignolet.