Whilst the Blades pussy-footed around, looking for something that after seven unbeaten matches in all competitions was just not there, Middlesbrough were producing perhaps their best performance of the season, capped off by emphatic first-half goals from Duncan Watmore and Paddy McNair.
So the team that appeared to have clicked lost, and the one that seems to have still been scrabbling around after a summer overhaul claimed only their third win of the season, 2-0.
Welcome to the Championship.
Neil Warnock is probably too long in the tooth to worry any more about pressure building on the terraces but he will have enjoyed his post-match drink at a Riverside that got fully behind his team far more than his opposite number Slavisa Jokanovic, grim-faced throughout.
The Blades saw 65 per cent of the ball, but only half of the eight shots on target.
When they did produce an excellent chance, through a wonderful George Baldock pass, muddled brains stopped them making the most of it.
Boro were far more clinical.
It was a game to remind the visitors they still have work to do even after their recent revival, and to reassure Boro supporters it is too soon to panic about their slow start.
Middlesbrough took the lead through their first shot of the match, 10 minutes in.
It was a goal worth waiting for, Sol Bamba spreading the ball out to Marc Bola, who exchanged passes with Matt Crooks.
Watmore was playing on the left of Boro’s 4-1-4-1 but far from hugging the touchline, giving Bola the space to attack and a passing option to as the left-back looked inside. His swinging finish was excellent.
Coming inside again, he produced a diving header from an Andraz Sporar cross.
Sheffield United had not got going at that stage. Morgan Gibbs-White’s early effort lacked sting and Ben Davies did well to recover his error after a poor pass put Oliver Norwood in trouble, tackle by Crooks.
On the rare occasions they got into dangerous positions, their decision-making was awry. They played some patient football when Ben Osborn collected a sweeping Norwood pass in the 19th minute but the extra thinking time had no benefit, the move breaking down.
John Fleck was lucky not to be punished for giving the ball to Marcus Tavernier, whose shot was not far wide.
When Iliman Ndiaye elegantly collected a good pass from Baldock he thumped against the post from a near-impossible angle rather than pull the ball back to Osborn, in a huge amount of space 12 yards out.
McNair, used in midfield, doubled the lead eight minutes before half-time when Sporar and Crooks helped a Bola cross into his pass for a resounding finish.
The managers played a bit of tactical chess in the second half, Jokanovic bringing David McGoldrick on in midfield to match Boro’s formation, so Warnock changed it to a left-side heavy 3-4-3.
The changes made little difference to the flow of the game.
Ndiaye had a look of resignation when he beat Lee Peltier only to kick the ball behind himself, and Gibbs-White one of frustration when he spun on a shot and put it just wide, unhappy it was his only real option.
Blades goalkeeper Robin Olsen saved from Sporar when Watmore fed the striker. Sporar was lucky that as the cards started to flow his was only a yellow.
It was a sensible decision from referee James Linington, who had done well to go back and book Fleck after a foul, but brushing Baldock’s hair with his forehead could have brought an over-reaction from some officials, particularly as it was in full view of the angry away fans.
McGoldrick only really came alive as a goal threat as the Blades piled forward in the final 10 minutes, Joe Lumley’s save even better than his shot, and centre-back Bamba making one of his own with his feet to cap an excellent performance from a rearguard which stood up to the tests the Blades were able to muster.
Striker Billy Sharp shot way over in the closing minutes and Fleck had an effort blocked in stoppage time but Boro were not to be denied.
Good all over the pitch, they had more than earned their victory, and Warnock had more than earned his post-match drink with friendly rival Jokanovic.
Middlesbrough: Lumley; Peltier, Bamba, Fry, Bola; Howson; Tavernier, McNair, Crooks, Watmore (Olusanya 78); Sporar (Ikpeazu 72). Unused substitutes: Hall, Payero, Lea Siliki, Daniels, Jones.
Sheffield United: Olsen; Baldock, Egan, Davies, Stevens (Norrington-Davies 69); Fleck, Norwood (McGoldrick 46); Gibbs-White, Ndiaye (Hourihane 77), Osborn; Sharp. Unused substitutes: Basham, Brewster, McBurnie, Foderingham.
Referee: J Linington (Isle of Wight)