Chelsea interim coach Rafael Benitez has risked sparking a fresh war with Alex Ferguson by appearing to question the Manchester United manager's "education".

The pair frequently clashed during Benitez's previous stint at Liverpool, and the bad blood was in evidence again during Sunday's 2-2 draw between the sides in the FA Cup quarterfinal at Old Trafford.

United led 2-0 through early goals from Javier Hernandez and Wayne Rooney, but the host took its foot off the pedal and Chelsea hit back through Eden Hazard and Ramires to force a replay.