Welshman David Cotterill celebrates after scoring from the spot
Sheffield United kept their slim automatic promotion hopes alive while ending Swansea City's play-off bid.
David Cotterill grabbed the winner from the penalty spot eight minutes before the break when Swans captain Garry Monk bundled over Stephen Quinn.
It could have been more had Dorus de Vries not pulled off fine stops from Darius Henderson and Chris Morgan.
Swansea got themselves back into contention in the second half but rarely threatened the United goal.
Sheffield United midfielder Gary Speed: "I thought we were excellent today, a team like Swansea coming here at this time is probably the worst team you want.
"We had to go long periods of the game without the ball... but the guys' discipline and attitude was brilliant.
"We worked their goalkeeper [Dorus De Vries] who made a couple of great saves and it could have been more."
Swansea manager Roberto Martinez: "The lessons that we've learned this campaign we should have performed better.
"But if you look at our season it's been an amazing success. We were in League One last season, we've got probably the lowest budget.
"But we've developed our own squad... I'm very, very proud."
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