United's U18s extended their unbeaten run to five games with a deserved home victory on Saturday.
An Oliver Greaves strike followed by own goal was enough for the Blades to secure all three points against Forest at the SteelPhalt Academy, despite playing the last half hour with ten-men.
The opening half an hour was a cagey affair with the only opportunities being a couple of speculative attempts from distance by the visitors.
However, it would be United who broke the deadlock in the 33rd minute, a long throw from Cantrill wasn't dealt with and GREAVES was there to guide the ball home first time on the half volley to put the Blades in front at the break.
Shortly after the restart, the Blades doubled the advantage in fortuitous fashion, a routine back pass was misjudged by the Forest goalkeeper and the ball rolled under his foot and into the net.
Just before the hour though, Portman was dismissed for a second bookable offence following a tackle that also injured team-mate and half-time substitute Mason.
As the clock ticked down, Warhurst was called into action on a couple of occasions to deny Forest. Firstly, from close range with a brilliant reflex save, then by pushing a free kick round the post to see the Blades home despite their numerical disadvantage.
Blades: Warhurst, Portman, Cantrill, Cutts, Ferguson, Belehouan (Mason 45, Kelly 57), Hawkes, Broadbent, Greaves, Ompreon (McClellen 62), Potts.
Unused: Dewhurst, Weaver.