United's U18s slipped to a disappointing defeat against Cardiff City in Wales on Saturday.
Coach Travis Binnion admitted that the Blades simply weren't at the races, but praised the performance of the Bluebirds, remarking:
"Cardiff are a really good footballing side and I was impressed by a number of their players, but we were poor.
"Take nothing away from the opposition though they deserved to win and could have done so by a greater margin.
"Nothing about us was at the required standard to give ourselves a chance and that is massively frustrating."
The hosts started the game positively and put the Blades on the back foot with a flurry of corners.
Then in the 7th minute, having hit the post in their previous attack, City took the lead, albeit after a blatant foul on Hinchliffe was missed on the halfway line.
The Bluebirds then had a goal disallowed for offside, prior to Cockerline getting in behind the home and deciding to stay on his feet and score rather than going down following a shirt tug in the penalty area.
Before half-time the injured Cockerline had to be replaced Kedman, with Calvert-Lewin moving up front to lead the line.
The second-half saw the Blades enjoy more possession and territory, but Cardiff were always in control and extended their lead in the 51st minute.
A mistake allowed Watkins a shot on goal which was blocked by Evans, but PHIPPS was on hand to fire home the rebound from close-range.
Wright, Calvert-Lewin, Hinchliffe all had chances to reduce the deficit but were denied by Massaro in the City goal.
Blades: Eastwood, Ishmail, Brown (Ramsey 69), Gordon, Evans, Semple (Cheeseman 55), Heh, Calvert-Lewin, Wright, Cockerline (Kedman 34), Hinchliffe.
Unused: Giraud-Hutchinson, Ramsdale.