Swansea City suffered defeat at the Swansea.com Stadium as Ken Sema’s ferocious late strike gave Watford victory.
The Swans had by far the better of the opening period, with captain Matt Grimes twice going close from distance and Harry Darling unable to make clean contact with a free header.
Kristian Pedersen thought he had given his side the lead when he headed home from a corner with 20 minutes to go, only for the Swans to be penalised and the goal chalked off, while Darling forced two fine saves from Daniel Bachmann in the Watford goal.
At the other end, Carl Rushworth made good saves to deny Tom Ince and Vakoun Bayo, but there was little he could do about Sema’s winner as the Sweden international walloped a left-footed strike into the roof of the net.
The Swans had shown three changes from the defeat to Leicester, Pedersen, Harrison Ashby and Jay Fulton came into the side, with Josh Tymon and Charlie Patino dropping to the bench, while Josh Key missed out through injury as 17-year-old Sam Parker was named among the substitutes.
The Swans missed an early chance when Jamie Paterson delivered left-footed into the box and Darling headed wide when free just outside the six-yard box.
Lovely interplay then worked Fulton into space, but his final pass for Jamal Lowe was cut out, while Rushworth made a smart save to deny Ince’s left-footed effort at the far post.
Lowe then had a volley blocked after Liam Cullen’s clever knockdown with the Swans firmly on the front foot.
Swansea continued to look the sharper, captain Grimes showing his alertness by causing Daniel Bachmann to scramble back towards goal as he tried an audacious chip from 40 yards.
Watford were prepared to sit off and invite the Swans on to them, and Grimes forced Bachmann into a fingertip save as his curling strike from Paterson’s lay-off threatened to find the far corner.
Pedersen headed the resulting corner back across goal but no white shirt could turn it in.
The Hornets were proving stubborn opponents, and they nearly snatched a half-time lead when Jeremy Ngakia’s cross found Bayo free at the far post, but Rushworth made a terrific save to deny the striker as the half ended goalless.
Wesley Hoedt headed a corner over the bar early in the second period for the visitors and Pedersen covered back well as Ince attempted to reach a loose ball running into the Swansea area.
Duff sent on Ollie Cooper and Tymon for Paterson and Cullen as the Swans switched systems.
Seconds later Darling made a crucial block as Mileta Rajovic took aim from a Yaser Asprilla cutback.
Pedersen then thought he had given Swansea the lead with 20 minutes to go when he rose to power home a header from a Grimes corner, but referee Andrew Kitchen cut short the celebrations as he adjudged there had been a foul committed to create space for the defender.
Instead the visitors would snatch the win when Sema unleashed a thunderous drive from the left edge of the penalty area that flew beyond Rushworth and into the top corner of the net.
There was still time for Darling to force a diving stop from Bachmann as he met a Grimes free-kick, with the Watford captain then parrying the defender's drive from the edge of the box with the hosts unable to find a late leveller.
Swansea City: Carl Rushworth, Kristian Pedersen, Jay Fulton, Harry Darling, Matt Grimes (captain), Jerry Yates, Jamal Lowe, Jamie Paterson (Ollie Cooper 61), Liam Cullen (Josh Tymon 61), Harrison Ashby (Liam Walsh 79), Bashir Humphreys.
Unused Substitutes: Andy Fisher, Charlie Patino, Nathan Tjoe-A-On, Kyle Naughton, Sam Parker, Cameron Congreve.
Watford: Daniel Bachmann (captain), Jeremy Ngakia, Francisco Sierralta, Wesley Hoedt, Jamal Lewis (Mattie Pollock 90), Tom Ince (Yaser Asprilla 62), Jake Livermore, Ismael Kone (Giorgi Chakvetadze 82), Vakoun Bayo (Mileta Rajovic 62), Matheus Martins (Ken Sema 46), Edo Kayembe.
Unused Substitutes: Ben Hamer, Imran Louza, Rhys Healey, Mattie Pollock, James Morris.
Referee: Andrew Kitchen
Attendance: 14,698
