Swansea edged into the Capital One League Cup semifinals after finally breaking down npower Championship side Middlesbrough with a late goal at the Liberty Stadium.
The Swans reached only a third semifinal in top-flight cup competitions in their 100-year history thanks to an 81st-minute own goal from Boro's Seb Hines.
Hines could not clear a Swansea corner as the Premier League side exerted sustained late pressure, and the ball flew off him and past Boro goalkeeper Jason Steele.
It put Swansea into the last four alongside Bradford - memorable conquerors of Arsenal - and Aston Villa, while Chelsea meet Leeds in the remaining quarterfinal clash next week.
Middlesbrough gave as good as they got for most of a low-key contest in front of a 15,000 crowd, as both sides lacked a sharp attacking edge and laboured for long periods.
But the Swans eventually added Boro to their list of Capital One scalps this season alongside Liverpool, Barnsley and Crawley, while the visitors were left to reflect on what might have been following their 12th successive away League Cup fixture.
Boro, League Cup winners eight years ago, made a bright start that underlined their status as Championship promotion hopefuls this season.
Swansea were pressed on to the back foot for most of an opening 15 minutes high on endeavour, but that offered nothing in terms of clear-cut scoring chances.
There was enough on show, though, to encourage Boro fans who made the 640-mile round trip, and skipper Grant Leadbitter went close with a 21st-minute effort that forced Swans goalkeeper Gerhard Tremmel into a save low at his right post.
Nathan Dyer's darting runs apart, Swansea produced little in the final third, much to manager Michael Laudrup's growing frustration as he prowled his technical area.
Even when Swansea gained their first corner of the match - after 32 minutes - Boro had little trouble clearing possession and settling back into a solid rhythm, punctuated only when Dyer deflected a half-chance straight at Steele.
Tremmel was then forced to react smartly to keep out a Leadbitter effort, and Boro boss Tony Mowbray was the far happier manager as half-time approached in a tie that never seriously threatened to move out of second gear.
Leadbitter, Boro's best player, was harshly booked by referee Lee Probert for a challenge on Ben Davies, and Swansea ended the opening 45 minutes with successive corners that did not trouble Steele or his defenders.
Boro started the second half brightly, with Justin Hoyte peppering Tremmel's goal from long range, and they continued to display greater energy, especially in the congested midfield area.
Swansea, in contrast, cried out for accuracy and urgency, and it was no surprise when Laudrup made his first change just 10 minutes after the break when he sent on Luke Moore to replace Itay Shechter.
And Moore was immediately in the action, challenging Boro defender Andre Bikey just outside the visitors' penalty area that ended with both players going down.
Bikey required treatment before he could continue, but even though he attempted to run off his injury, it was to no avail. Faris Haroun also departed for Boro, with Andrew Halliday and Richard Smallwood going on.
Laudrup also made a second switch, with Ki Sung-yueng going on for Wayne Routledge, but there was still no sign of the deadlock being broken.
Swansea, though, started to string some attacking phases together, and they went agonizingly close 15 minutes from time after Nicky Bailey was cautioned for bringing down Dyer.
Jonathan De Guzman took the resulting free-kick, and Steele palmed it on to the crossbar, keeping Boro level, although pressure continued to mount with Michu a consistent threat.
Referee Probert then waved away Swansea claims for a penalty when Hines challenged Ki, and a game that had previously lacked an attacking flow suddenly opened up.
Boro could only survive such sustained pressure for so long, and the unfortunate Hines diverted the ball beyond Steele from a corner under pressure from Garry Monk as Swansea went ahead to ultimately secure a last-four place.
