The young defender’s impressive volley after 22 minutes was added to by Pablo Hernandez shortly before the final whistle as he fired home a loose ball in the West Brom area.
And after a mid-week battle in the UEFA Europa League, Michael Laudrup’s men showed no signs of fatigue as they dominated their hosts to clinch their vital first three points of the Premier League season.
Nicolas Anelka made his return to West Brom's line-up, following the death of a close friend that had seen him consider retirement according to manager Steve Clarke. Fellow newcomer Scott Sinclair made his league debut for the Midlands side.
Swansea opted to switch things up, making six changes from their UEFA Europa League defeat to Petrolul Ploiesti on Thursday.
The alterations looked to have been most advantageous for the visitors in the opening minutes, as Michael Laudrup’s men fired a number of efforts on goal with a free-kick from Jonjo Shelvey drifting over the bar.
James Morrison's header was nervily cleared away as the hosts looked to grab a foothold in the game, but they could not hold off the Welsh side, who went ahead on 22 minutes.
Pablo burst down the right and clipped a cross into the area with Davies latching onto it and lashing a wondrous volley past Boaz Myhill.
Wilfried Bony had a chance to double Swansea’s advantage minutes before the break, but the 24-year-old saw his effort comfortably scooped up by Wales international Myhill.
And despite making a change at half-time, which saw Graham Dorrans replace Morrison in a like-for-like switch, Swansea came out for the second in the same vein as they ended the first.
It was Wayne Routledge who had the chance to extend their advantage within three minutes as he tore down the wing, but a slightly heavy touch cost him as Myhill managed to keep him out.
The frustrations then continued to heap up for the hosts, with Anelka growing increasingly more agitated as his impressive work-rate continued to reap no rewards as the home side struggled to organise themselves.
And it only got worse from there as less than a minute after, Pablo saw an effort bounce off the crossbar, but was unperturbed a minute later as he found the back of the net after picking up Michu's clever cut-back into the area.
Clarke's side remain without a league goal this season, with just a point to show from their opening three games, while Swansea climbed off the bottom of the league with their first triumph.
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