United's U21s ended 2014 with a disappointing defeat against Leeds United at Thorp Arch on Monday afternoon.
Despite taking the lead through Connor Dimaio, the Blades conceded four goals without reply, including three in the second-half.
After an even opening it was the visitors that struck the first blow in the 19th minute, with DIMAIO finishing nicely following some good passing the build-up.
But the lead only last 11 minutes as MONTENEGRO capitalised on some indecision to level for the hosts.
Before half-time, in blustery conditions, skipper Terry Kennedy nearly restored the Blades lead.
Leeds were quickly out of the blocks in the second-half though and in the 53rd minute DAWSON fired the home side in front, despite the best efforts of George Long.
Moments later Wright was introduced in place of Paling as the Blades changed formation, but in the 75th minute, Leeds made sure of the victory with MONTENEGRO applying the finish to a swift counter attack.
Calvert-Lewin replaced Kieran Wallace with just over ten minutes remaining, but it was Leeds who added a fourth goal through PARKIN to cap a miserable second-half for United.
Blades: Long, Banton, Paling (Wright 59), Dimaio, Kennedy, Berry (Evans 84), Hamilton, Whiteman, McDonagh, K. Wallace (Calvert-Lewin 79), Khan.
Unused: Heh, Eastwood.