Three second-half goals condemned Blues to defeat in South Wales.BCFC
A dogged and resilient performance up to that point counted for nothing as Swansea capitalised in clinical fashion.
Substitute Kyle Naughton fired in the opener in the 63rd minute before an error allowed Swansea to expose Blues and score again, through Bersant Celina.
To add to the misery, Borja Baston stuck away a 75th minute penalty after a Marc Roberts foul as the hosts again took advantage of Blues attempting to find a way back.
Blues set up in a dogged 3-5-2, with Fran Villabla to the left in midfield rather than behind the front two as he was in midweek.
Knowing Swansea's strengths, it was a system designed to frustrate with a nod to what happened last time out on the road at Nottingham Forest.
By and large, Blues defended in and around their box very well in the first period.
In the seventh minute Harlee Dean provided a crucial, close range block to deny Yan Dhanda, who was teed-up in a good position by Andre Ayew.
And in the 34th, Kristian Pedersen was in the right place to head away Dhanda's curling attempt from the line after Swansea broke through.
Borja Baston may have been better off shooting when the ball came to him on the left of the area, but he opted to try and get a better angle
for a colleague, which allowed Blues to scurry back and close him, and get players alongside Lee Camp.
In between, Lukas Jutkiewicz had a shot charged down after he checked back onto his left peg outside the area, following Alvao Gimenez gaining a loose pass.
But that apart, there was little else that truly threatened Camp in the opening 45 minutes, whilst Blues could have taken care of the ball better when advancing.
Half-time: Swansea 0 Blues 0
Blues carried on where they left off after the break, with the first moment of alarm coming in the 56th minute when Camp made an outstanding tip over save to deny Baston's strong header from Matt Grimes' free-kick.
Blues made a change soon afterwards, bringing on Gary Gardner for Gimenez which resulted in Villalba moving centrally to support Jutkiewicz.
Then the game changed completely, when Swansea took the lead from Naughton's opportunist effort from the edge of the area.
There were still penalty appeals swirling in the air - Swansea felt Roberts pushed Baston as he headed clear - but it mattered not as Naughton got the loose ball and fired it quickly and low towards the near post, catching Camp who did get a hand to it.
Blues strived to get back into things, worse was to follow five minutes later when Villalba came deep to collect a short pass and was promptly bundled out of possession by Jay Fulton.
That left the Blues defence exposed, Fulton played a simple pass to the edge of the area for the free Celina, and he lashed the ball into the roof of the net powerfully.
In the 75th minute, Swansea added a third through Baston, who sent Camp the wrong way, planting the ball low to the right corner.
The spot-kick was awarded after Swansea got in down the right, Connor Roberts thumped the ball back low and as Dhanda latched onto it, he was caught as he went past Roberts.
Blues had been waiting to make a double substitution, when they eventually managed to do so, Jude Bellingham entering the fray became the Club's youngest ever player in the league.
Fortunately, such a margin to retrieve, it was a near possible task for Blues, who created half openings but the ball would not break their way.
A second successive 3-0 away defeat was all that was left to show from a long lunchtime trip to South Wales.
Full-time: Swansea 3 Blues 0
Swansea (4-2-3-1): Woodman, Roberts, Bidwell (Naughton ht), van der Hoorn, Rodon, Fulton, Grimes, Ayew, Dhanda (Byers 83), Celina
(Garrick 83), Borja. Subs not used: Nordfeldt, Routledge, Surridge, Wilmot.
Goals: Naughton (63), Celina (68), Baston pen (75)
Booked: Naughton (82)
Blues (3-5-2): Camp, Dean, Roberts, Pedersen, Harding, Sunjic, Davis (Bellingham 76), Seddon (Crowley 77), Villalba, Gimenez (Gary Gardner 57), Jutkiewicz. Subs not used: Stockdale, Medina, Bailey.
Booked: Davis (49), Pedersen (60), Seddon (73), Sunjic (88), Bellingham (90+3)
Referee: A Woolmer
Attendance: 17,277 (1,444 Blues fans).