A young Blades side fell to a defeat against Blackburn Rovers as the Premier League Cup got underway again.
Looking for a win that would all but seal progression to the next round, United found it difficult to cope with an excellent Blackburn performance and never recovered from conceding two early goals.
The first 10 minutes brought pressure from the hosts but bar one routine save from Jordan Amissah there was little for the Blades to worry about in the opening exchanges.
But two quick-fire goals ensured United were always chasing the game. Matty Platt bundled home a corner to make it 1-0 and no more than a minute later Sam Graham conceded a penalty for a foul inside the box.
All of a sudden United found themselves two down as Dan Butterworth hammered the resulting spot kick past Amissah.
Oliver Greaves' free-kick from the edge of the box which was blocked by the Rovers wall was about the closest United came during a difficult first save and Blackburn missed several glaring chances before adding a third before the break.
Butterworth was the scorer once again, this time running deep into United's half and smashing a shot home from the edge of the box.
United introduced Harrison Neal and Tom Williams at the break to look for a response and the Blades certainly gained more of a foothold in what was a relatively uneventful second half of the match.
Both sides saw efforts blocked but neither could really produce any clear goal scoring chances with the hosts happy to hold onto the ball and settle on their 3-0 lead.
Blades: Amissah, Gordon (Williams 46), Belehouan, Broadbent, Graham, York, Ferguson, Greaves, Mallon (Ackroyd 79), Brunt (Neal 46), Sheppeard.
Unused: Dewhurst, Gomis.