Peterborough, Carlisle and Oldham all blew chances to leapfrog Sheffield Wednesday at the top of npower League 1 after failing to win games against struggling opponents on Saturday afternoon.
Posh dropped from second place to fourth after going down 1-0 at Tranmere, who recorded their first league victory of the season to haul themselves out of the relegation zone.
Arnaud Mendy was the home side's hero with his first goal in English football, the French midfielder sidefooting home shortly before half-time following good work from Ryan Fraughan.
Carlisle climbed above Peterborough into second place despite being held to a goalless draw by Swindon, who are still looking for their first league win this term.
It could have been worse for United had Charlie Austin not volleyed against the crossbar in the first half or blazed over in stoppage-time when clean through, those missed chances seeing the Robins slip to second bottom of the table.
Injuries and international call-ups forced Oldham player-manager Paul Dickov to hand himself a debut, but his substitute appearance could not prevent his side being held to a 1-1 draw by Bristol Rovers.
Will Hoskins put Rovers ahead early on before Chris Taylor levelled on the stroke of half-time.
But despite a second yellow card for the visitors' Danny Coles, the Latics were unable to force a win - although they did preserve their unbeaten record.