Nigel Clough says individual errors proved costly as United slipped to an unfortunate 2-1 defeat to Bristol City on the opening day of the Sky Bet League One season at Bramall Lane.
Aaron Wilbraham headed City in front, before Michael Higdon replied with his first goal in red and white, only for midfielder Wade Elliott to grab the winner in the second period.
Looking back, the Gaffer remarked: "We are disappointed with the nature of the two goals we conceded, although we also played a lot of good football and created a number of decent chances.
"We played well in parts but it is going to be very difficult to win matches when we are conceding goals in the manner we did.
"For the first goal we gave the ball away unnecessarily in midfield and as a team we didn't recover. The second goal is poor again. We haven't tracked a runner from midfield and both goals are uncharacteristic for us really.
"The game went flat in the second-half and that suited Bristol City. We wanted to carrying on playing at a high tempo and with momentum, but they managed to control the game as it went on, but a mistake ultimately cost us the game and that is disappointing.
"We could have still nicked an equaliser on another day, though, so we won't get despondent."