Poor defending and missed opportunities proved costly as United's youngsters ended a frustrating campaign with a 3-1 defeat against Newcastle at Shirecliffe.
Harry Maguire scored a late consolation but the Magpies had already put the game to bed, capitalising on several moments of indecision amongst the Blades backline.
The home side started out on the front foot, Gregory firing over when well placed, but in the 18th minute United lost possession on the right and were made to pay as a well timed through ball enabled the visitors to take the lead.
The Blades responded well and had all the play, with Roe, Gregory and Chappell industrious down the flanks, but more poor defending gave Newcastle a second before half-time.
The start of the second period had remarkable similarities to the first, Foster shooting straight at the keeper when well positioned, before Chappell failed to convert after turning his marker.
Gregory put in a pinpoint centre that nobody got on the end of, before Pomares headed wide from Roe's left-wing delivery. Despite all the pressure United fell three behind in the 58th minute.
Slew, Foster and Ahmadi all wasted openings, before Maguire rose highest from a free-kick to restore some pride for the Blades.
Coach Kevin Fogg was again frustrated by the Blades inability to convert numerous openings, but drew a crumb of comfort from the U16s success over the same opposition:
"Once again, not for the first time, we have ultimately paid the price for missing chances and not defending well enough. We have lacked that cutting edge throughout the campaign and it has been disappointing.
"On a positive note the U16s beat Newcastle 4-2, so that bodes well for the next crop coming through."
Blades: Andrew, Brown, Roe, Maguire, Darlow, Pomares, Chappell (Lammy 75), James, Foster, Wilkinson (Slew 60), Gregory (Ahmadi 60).
Unused: O'Kane, Pennycooke-Morgan.