Sakho was one of two players brought on with 10 minutes remaining, a tactical switch that paid off for West Ham manager Slaven Bilic and brought relief and three points to the home side.
West Ham striker Andy Carroll hit the crossbar five minutes from time before Sakho stole in at the far post to lift West Ham out of the relegation zone.
The goal was the first Swansea have conceded away from home in the league this season and defeat left them in the bottom three.
"It is a relief, a great three points for us," Bilic told the BBC.
"We did not play well in the first half after a good first 10 minutes, making basic mistakes and Swansea were much better on the ball. We have to play better and we can play better.
"The changes were crucial with Manuel Lanzini, Arthur Masuaku and Diafra Sakho coming on," he added.
"We played a very offensive formation in the first half but lacked the link between the defence and attack and that was why Lanzini made a big impact."
(Reporting by Sophie Hurcom, editing by Ed Osmond)
Share
