Town boss Joe Royle was unhappy at referee Eddie Ilderton's failure to award either of two penalty calls for handball by Blades' defender Chris Morgan.
Royle said: "We are all bitterly disappointed, particularly with Morgan's handball in the last minute.
"The linesman was just 15 yards away, while for the one in the first half Morgan has put his hand in the air to deflect the ball away.
"We should have had two penalties, yet they get an obligatory one but in the end 1-1 is fine with us.
"We've still got to win our last game and bearing in mind Wigan have to play West Ham in their final game, we would have settled for this.
"After being bottom of the table following our first six games, to be in this position with one game to go and just needing a win to make the play-offs is not bad."
Blades' boss Neil Warnock says his side's play-off chances have gone: "I should be saying the right things, such as, 'While it's mathematically possible we will give it our best shot.'
"But, for me, we've no chance now. You don't get the results that we now need. I am not that much of an optimist.
"It has been frustrating over the last six weeks. It is clear we have not been good enough.
"I have been here for four and a half years now and every two years or so we have had to change things and it's that time again.
"We are at the stage where we've got one or two young lads coming through and there are one or two Bosmans I can pick up in the summer.
"I believe Sheffield United fans can look forward to an exciting future."