United appealed last week after McNamara was hit with an immediate three-game ban, with two more suspended, following a spat with St Johnstone manager Tommy Wright.
That allowed McNamara to take his place in United’s semi-final victory over Rangers but, with five games left in the Premiership season, the appeal risked delaying the former Celtic player’s ban until the clash with the Perth club on 17 May.
A club statement read: “We firmly believe that there are solid grounds to appeal the sentence imposed. However having given the matter further thought and as no hearing date has yet been fixed, we now believe it is in the best interests of all concerned to accept the sentence imposed and withdraw the appeal.”
McNamara was found guilty of misconduct by the “repeated use of offensive, insulting and abusive language” while Wright was given a suspended one-match ban for “leaving the technical area in the absence of special circumstances and by adopting a threatening and aggressive attitude towards an opposing member of team staff”.