Gavin Henson scored 10 points in three minutes shortly after coming on as a second half replacement to steer Swansea to a stunning victory over arch-rivals Neath at St Helen's.
Having lost Arwel Thomas to the sin-bin for a deliberate knock on early in the second half, Swansea threw on Henson to take over at No 10.
The Welsh international turned the game with some astute tactical kicking followed by a close range try which he also converted.
That hauled Swansea back into the lead after they had seen their 10-0 interval advantage turned into an 11-10 deficit as Neath came powering back into contention after a poor first half.
Swansea went off at a cracking pace and Wales prop Ben Evans rolled over in the opening minutes to score a try which Thomas converted. Thomas added a penalty before the break to extend the home lead.
But no sooner had the second half begun than Neath wing Shane Williams slipped over in the left corner for a try and then two penalties from the boot of replacement outside half Shaun Connor put the visitors ahead for the first time.
That was the moment for Henson to strike and, after giving Swansea a good position close to the Neath line with a superb kick, he crashed over for a vital try which he also converted to make it 17-11.
Obviously on a roll, the young outside half then completed his spectacular contribution by dropping two goals to secure victory and leave Neath with a few problems ahead of their Celtic League semi-final clash with Cardiff at The Gnoll on 4 January.
Scorers: Swansea: Tries: B Evans, G Henson; Cons: A Thomas, G Henson; Pen: A Thomas: DGs: G Henson 2. Neath: Try: S Williams; Pens: S Connor 3.