United's youngsters slipped to a disappointing home defeat to Millwall.
Coach Travis Binnion was quick to acknowledge the Blades were well below par, remarking:
"We were on the front foot for the first 10-15 minutes, but after that Millwall fully deserved their victory.
"They defended better than we did and going forward caused us a lot of problems. We didn't pass the ball anywhere near well enough and we gifted Millwall their goals and numerous other opportunities.
"We need to work hard prior to the Ipswich fixture on getting the basics right because we weren't good enough and the performance was out of character."
United started brightly and Heh had the first chance after an excellent through ball from Calvert-Lewin, the winger failed to get his shot away and the ball was cleared for a corner, from which Cheeseman saw his header cleared off the line.
United attacked quickly after but Kedman's inviting centre evaded everyone and from this moment, Millwall grabbed the game by the scruff of the neck.
The Blades gave away possession deep inside their own half and were duly punished in the 35th minute, moments later Ramsdale had to make an excellent save to keep the score at 1-0 going into the break.
The second-half was pretty much one-way traffic with the Lions in the ascendency. Chances came and went for the visitors with Ramsdale making several fine saves.
But United's goalkeeper handed Millwall the chance to doubled their lead late on when he gave away a penalty which was subsequently converted.
Another defensive slip handed the visitors a third in the latter stages to cap a disappointing performance from the Blades.
Blades: Ramsdale, Hinchliffe, Kelly, Ishmail, Adebowale (Hutchinson H/T), Cheeseman, Heh, Calvert-Lewin, Cockerline (Slew 59), Hallam (Wright H/T), Kedman.
Unused: Semple, Eastwood.