Chelsea largely controlled the match, but were guilty of missing the few chances they created, while Swansea were contrastingly lethal when presented with an opportunity in each half from the Serbian defender.
Already having gone further than ever before in the League Cup, Swansea now must be confident of achieving a place in the final and capping what has already been a hugely impressive first season under Michael Laudrup.
With Wembley just two matches away, both managers elected to field strong lineups as Michu returned up front for Swansea, while Chelsea went for the attacking midfield trio of Juan Mata, Oscar and Eden Hazard.
David Luiz also continued in his central midfield role and, combined with the trio ahead of them, he was influential in giving Chelsea their early dominance.
It was a delightful move by the home side that gave them the first of two presentable chances in the opening period. Both Luiz and Hazard were involved as Ramires was played through down the right of the area, but after delaying and delaying the midfielder produced a tame shot that was saved by Gerhard Tremmel.
Despite an early warning from Michu of the threat he posed even isolated as he was up front, Chelsea continued to look the side far likelier to make the breakthrough. Mata saw his shot blocked by the head of Ben Davies before Gary Cahill headed over from Oscar’s corner.
Then in the 26th minute came Chelsea’s best chance of half and, as it would turn out, the match. The Swansea defense parted in front of Hazard as he glided toward the edge of the box before squaring it to an unmarked Mata who produced a poor side-footed shot straight at Tremmel.
Mata came close again as Oscar found him with a brilliant flick, but the Spaniard dragged his right-footed shot just wide of the far post.
It was looking a matter of time before Chelsea took the lead, but Swansea hit Chelsea with a classic sucker punch six minutes before the end of the first half. Ivanovic’s poor touch on the edge of his own box allowed Jonathan de Guzman to sneak in and the ball ran to Michu who took a touch and produced a now familiar lethal finish curled into the corner form the edge of the box.
It was a rare error for the usually solid Ivanovic and the frustration appeared clear as he immediately attempted to redeem himself with a surge up field. He produced a fine turn and then powerful shot from 20 yards out that forced Tremmel to dive and palm it past the post.
The second half continued in much the same vein, although, with Swansea increasingly content to focus on holding what they had, Chelsea will be disappointed with the number of times that they threatened their opponents’ goal. To that end they were not helped by another listless performance by Fernando Torres, who was eventually replaced by new signing Demba Ba.
Chelsea’s lack of bite up front was perhaps summed up by the fact that Luiz provided the greatest threat to bringing Chelsea level.
The wild-haired Brazilian struck a trademark dipping free-kick from a central position over 30 yards out that had Tremmel scrambling across but the dipping effort went wide of the post. Tremmel was forced into action minutes later from the same opponent. Chelsea worked the ball through and Mata laid the ball back to Luiz whose powerful left-footed shot was well held by the German.
With Michu cutting an increasingly isolated figure up front, Chelsea began to build up some pressure midway through the second period. Swansea boss Laudrup, likely fearing the increasing pressure his side was coming under, looked to shore up his side’s defenses by bringing off Wayne Routledge for defender by trade Dwight Tiendalli.The gauntlet had been laid down to the home side to produce something special to get an equalizer. It was a challenge that they were not equal to.
But, while Chelsea failed to create a clear opportunity, Ba did provide more impetus up front in his 10 minutes on the pitch than Torres had in the previous 80.
Ba threatened with two headers, the first of which was too close to Turnbull and the second that went just wide of the post. Then, just seconds after the Senegalese front man was booked perhaps harshly for a dive, Swansea again struck out of nowhere.
Ivanovic failed to check before laying a pass back to his keeper and substitute Graham took full advantage of a second sloppy moment as he took the ball around Turnbull and then slid a shot into the net as defenders closed down on him.
Chelsea will feel that they should be heading to Wales in two weeks’ time with just a one-goal deficit to overcome as Ba saw an effort ruled off for offside in injury time when he appeared level with the last defender.