Swansea City suffered a first Championship defeat in four games as a Josh Tymon own goal saw them edged out by Sheffield United at Bramall Lane.
The Swans left-back was unable to adjust to clear a Harrison Burrows cross in the final moments of the first half, diverting the ball into his own net for what proved to be the only goal of the contest.
The visitors made it a challenging evening for the unbeaten hosts – who were relegated from the Premier League last season and are fancied for an immediate return – particularly in a first half where they subdued the home crowd and had spells of control.
Just prior to Tymon’s own goal, they had created a great chance for Myles Peart-Harris, while there were several other moments of promise they could not make the most of.
The hosts had the better of the second period, striking the woodwork twice and seeing Lawrence Vigouroux make a handful of important stops, but had some nervy moments during the closing stages.
Swansea boss Luke Williams will be frustrated by defeat, but will again have seen reasons for optimism in how his side the bravery he had known they would require in a hostile atmosphere.
With this being the second game of three games in the space of six days, Williams opted to make changes as Peart-Harris was handed his first Swans start, and Josh Key and Jay Fulton came into the side with Žan Vipotnik, Kyle Naughton and Gonçalo Franco dropping to the bench.
It proved an even start, although Vigouroux made the first save of the night when he got down quickly to save from Tyrese Campbell, before Harry Darling was unable to make the most of a free header from a Jisung Eom corner at the other end.
A sweeping Swansea move then took the play from one end of the field to the other, ending with Ronald cutting inside and seeing a shot deflected wide for a corner.
The home crowd were growing frustrated and that only increased when Campbell hung up a cross to the far post that was beyond the reach of Andre Brooks, who was unmarked at the far post.
Jamie Shackleton saw a strike blocked away for a corner after good work from Gustavo Hamer and Sydie Peck, with Ahel Ahmedhodzic heading the resulting set-piece wide at the near post.
But Swansea crafted the best chance of the half, moving the ball swiftly from back to front where Cooper picked out Peart-Harris’ run with a wonderful cross, but the loan man could only steer the ball wide.
And the miss proved costly as a deep cross from the left by Burrows was turned into his own net by Tymon as he attempted to clear, and the Swans trailed at the interval.
It was harsh on the visitors but they started the second half well, controlling possession and dictating play.
But the next big chance went the way of the hosts as Brooks won the ball on the edge of the box and bore down on goal.
Vigouroux saved brilliantly before Campbell’s follow-up effort struck the underside of the bar and bounced away from goal for Ben Cabango to clear.
The Swansea keeper denied Brooks again a few moments later before the woodwork came to the visitors’ rescue as Kieffer Moore struck the post after getting behind Darling.
Swansea lifted the pressure and had good spells of possession in the Blades’ half, but were finding it hard to create clear-cut opportunities.
Tymon sent in a threatening cross that Michael Cooper punched away as the final 20 minutes approached, while Darling headed a Matt Grimes free-kick over the bar, although it would not have counted as the referee adjudged a foul had been committed.
Blades keeper Cooper then parried away a driven Grimes free-kick in the final moments, before Vipotnik nodded a Florian Bianchini cross into the ground and wide of the target.
Swansea City: Lawrence Vigouroux, Josh Key, Ben Cabango, Harry Darling, Josh Tymon (Kyle Naughton 77); Matt Grimes (captain), Jay Fulton (Joe Allen 72), Ollie Cooper (Žan Vipotnik 64); Ronald (Florian Bianchini 64), Myles Peart-Harris, Jisung Eom (Azeem Abdulai 72).
Unused Substitutes: Jon McLaughlin, Gonçalo Franco, Nathan Tjoe-A-On, Nelson Abbey.
Sheffield United: Michael Cooper, Harry Souttar, Gus Hamer (Rhian Brewster 72), Callum O’Hare (Rhys Norrington-Davies 84), Harrison Burrows, Anel Ahmedhodzic, Jamie Shackleton (Alfie Gilchrist 58), Vini Souza (captain), Tyrese Campbell (Kieffer Moore 58), Andre Brooks (Jesurun Rak-sakyi 58), Sydie Peck.
Unused Substitutes: Adam Davies, Sam McCallum, Femi Seriki, Billy Blacker.
Referee: Leigh Doughty
Attendance: 25,112