Midway through the first-half, long before Oliver McBurnie scored the only goal of the game, Oliver Norwood prepared to take a free-kick on the edge of Swansea City's penalty area after being upended by Leroy Fer.
The midfielder paused to assess his options. The Liberty Stadium held its breath. But the resulting shot, as Chris Wilder fidgeted anxiously on the touchline, flew straight into the wall and ricocheted to safety.
Those 30 seconds of promise, which ultimately came to nothing, perfectly encapsulated the visitors's performance and explained why their hopes of recording a fifth straight league win were dashed by Graham Potter’s side.
"If we'd scored when we were on top it would probably have been different" Jack O'Connell, the United centre-half, said. "We knew it was going to be tight and, at the break the gaffer told us that the first goal would probably settle it."
Defeat does not sit comfortably with either O'Connell or Wilder, who cut a conflicted figure afterwards.
The United manager, having watched his team refuse two golden opportunities during the game itself and therefore one to move onto the shoulders of Championship leaders Leeds, was frustrated by their wastefulness in the final third.
But, assessing the state of play in a competition of ridiculously fine margins, the perseverance they displayed, combined with some enterprising approach play, tempered his disappointment.
O'Connell, the most impressive player on the pitch, also took solace from the fact United demonstrated the physical and psychological qualities required to maintain a promotion challenge.
Even if, on this occasion, they fell just short.
"We were looking at their team sheet to begin with," O'Connell continued. "There's lots of quality there.
“So in a sense, even though we're not happy with how things turned out, we can take something from the fact we gave them so much to think about, a really good test and are unhappy not to have got the win."
STILL WELL PLACED
It speaks volumes about the progress Wilder's squad have made in recent months that, less than two years after lifting the League One title, they departed South Wales third in the table and staring down at the likes of Middlesbrough, Derby County and West Bromwich Albion.
Swansea, who were playing top-flight football only a season ago, are another club in United's slipstream despite boasting numerous internationals and a former Ajax defender among their ranks.
It was the latter, Mike van der Hoorn, who found himself at the centre of controversy during the closing stages when he appeared to handle in the box.
Referee John Brooks, whose decision making appeared to anger Wilder more than the result, remained unmoved though meaning McBurnie's finish, from Nathan Dyer's tantalising cross, settled a contest of two distinct halves.
"We gave it our all and tried to force the initiative," O'Connell insisted. "Even at 1-0 down, I thought we were the ones trying to force things."
Before Gary Madine made his debut and fellow loan signing Kieran Dowell was introduced, United had seemed destined to enjoy a profitable evening as they scythed through Swansea's midriff and controlled the opening period.
The trouble was, by the time Potter's men discovered their own rhythm following some intelligent strategical changes, two glaring misses meant United had not made it count with Billy Sharp and his fellow centre-forward David McGoldrick both failing to score from close-range.
WHAT MIGHT HAVE BEEN
Wilder demonstrated his own tactical flexibility by making numerous adjustments too as his side searched for a route back into the contest following McBurnie's intervention.
Dowell and Madine both impressed after entering the fray, with the latter in particular suggesting he will prove a shrewd acquisition.
But with Swansea improving after the interval, as Dyer's influence grew on the game, they were left wondering what might have been.
"We just got a little bit sloppy for 10 minutes," O'Connell conceded. "We paid the price for that. It's a lesson and one we'll learn from."
After a chess-like opening, which saw both teams size each other up from a distance, a match began to break out when George Baldock fired over the crossbar and Sharp, seemingly forgetting Erwin Mulder was present, tried to caress the ball home from the edge of the six yard box rather than power it beyond the Swansea goalkeeper.
It was a rare error of judgement from United's captain, who has scored 17 times since August, and compounded by McGoldrick's piece of profligacy just before the interval; heading wide of the post after stooping to meet Mark Duffy's pass.
McBurnie was in much more ruthless mood and, having seen Matt Grimes go close, netted his third goal in as many outings against United following a spell of Swansea pressure.
Dean Henderson, who later made an excellent save to deny substitute Daniel James, was powerless to prevent the ball nestling in the back of his net.
"We'll dust ourselves down and move on," O'Connell said. "Because there's a big prize to play for."
Swansea City: Mulder, van der Hoorn, Fer, McBurnie, Celina, Dyer (Fulton 82), Routhledge (James46), Grimes, Rodon (Carter-Vickers 20), Roberts, Naughton. Not used: Nordfelt, Montero, McKay, Baker-Richardson.
Sheffield United: Henderson, Basham, Egan, O'Connell, Baldock, Stevens, Norwood, Fleck (Madine 74), Duffy, Sharp, McGoldrick (Clarke 82). Not used: Moore, Coutts, Stearman, Johnson.
Referee: John Brooks (Leicestershire).