It said much that Sunderland, despite trailing for the vast majority of the game, did not have a shot on target until stoppage time.
Jack Rodwell headed home a fine Callum McManaman free-kick, but by then the game was up. The narrow scoreline did not reflect a game that had the vast majority of the home support leaving long before the final whistle.
This was a listless, insipid display in which a recently promoted side coasted to a 2-0 win, courtesy of a brace for debutant Clayton Donaldson.
The hosts were booed throughout the game in an eerie reminder of the closing stages of last season. After the positivity of the 1-1 draw with Derby on the opening night, Sunderland have gone backwards quickly and dramatically.
The Black Cats had started the game by matching Sheffield United's 3-4-1-2 system, a number of players taking up unfamiliar roles. With two debutants, there was an obvious, disjointed look about Sunderland.
Neither side created much in a turgid first 20 minutes, but it was all too easy for the visitors who scored with their first counter-attack of the game.
New signing Clayton Donaldson found himself in acres of space on the right, cutting inside Marc Wilson too easily and shooting past Robbin Ruiter at his near post. Sunderland did force their first attempts of the game soon after, but both Jonny Williams and Lewis Grabban fired well over the bar.
A restless crowd bemoaned an insipid performance from the hosts, who were badly lacking cutting edge and playing too many aimless long balls in possession.
They did go close when James Vaughan volleyed Grabban's cross wide, but the chorus of boos that greeted the first time whistle reflected arguably the poorest half of the season. It did not improve.
Ruiter had been a spectator in the Sunderland goal, other than picking the ball out the net following the opener, but the Blades were quite comfortable with that as it was the same story with Jamal Blackman at the other end.
United were challenging the Black Cats to open them up on their home ground and other than some bright touches from Jonny Williams, they never threatened to do so. John O'Shea had replaced Lamine Kone at the break, with Callum McManaman replacing Vaughan shortly after.
The winger did make an instant difference, and Sunderland felt they should have had a penalty when Williams was nudged away from an inviting cross.
From there the game followed a predictable pattern, however, the hosts picked off on the counter as Donaldson ran clear to score the second.
The mood was ugly, the ground quickly emptying, an understandable reaction to a dismal showing that will have alarm balls ringing. Rodwell's consolation added gloss to the scoreboard that in truth Sunderland did not deserve.
Sunderland XI: Ruiter; Wilson, Browning, Kone (O'Shea, 45), Galloway, Honeyman (Gooch, 70); Rodwell, Ndong, Williams; Grabban, Vaughan (McManaman, 67)
Unused Subs: Steele, Jones, McManaman, O'Shea, Matthews, Gibson
Sheffield United XI: Blackman; Freeman, O'Connell, Basham, Wright, Stevens; Coutts, Fleck; Duffy (Lundstram, 67), Donaldson (Evans, 78), Sharp (Brooks, 67)
Unused Subs: Eastwood, Baldock, Carter-Vickers, Lafferty,