By Chris Harris at Liberty Stadium
Arsenal and Swansea City will have to do it all again on January 16 after their thrilling FA Cup tie ended in a draw.
In a breathless, topsy-turvy second half, Arsène Wenger looked to be heading for his first third-round defeat as Arsenal manager and then seemed set for a fourth-round trip to Brighton before the spoils were shared.
Michu, the scourge of the Gunners at Emirates Stadium in December, came off the bench to roll in the opener just before the hour mark.
It was harsh on Arsenal, who had dominated after a low-key first half, but they dug deep and came up with two special goals in the space of three minutes.
Lukas Podolski span and fired low into the bottom corner with nine minutes remaining and Kieran Gibbs smashed a stunning volley into the roof of the net to complete the turnaround.
The left back's collector's item could and should have been decisive but Danny Graham swept home an equaliser with four minutes left.
This was a slow-burner of a cup tie which came alight in the last half-an-hour, and Swansea were indebted to goalkeeper Michael Vorm for two sharp saves to deny Olivier Giroud - plus a brilliant stop to thwart Laurent Koscielny in the final seconds.
With time running out everyone of an Arsenal persuasion would have taken a draw. Ultimately, the prospect of a Wembley appearance in May remains alive.
It's a bit premature to talk about Swansea as a 'bogey team' but Arsenal's recent record against the Welsh club has not been good. They lost here by the odd goal in five last season and were undone by two late Michu strikes in December.
So it was a relief to see their Spanish tormentor out of the starting line-up for this game. Swansea manager Michael Laudrup shuffled his pack with a Capital One Cup semi-final on the horizon, giving Kyle Bartley his second start since joining the club from Arsenal last summer.
During his pre-match media work Wenger made it clear that he wanted to see "a different Arsenal" to the one that succumbed to Swansea last month and he would have been pleased with his side's brisk start. With Theo Walcott stationed close to Giroud there were shades of 4-4-2 about the Arsenal formation and they linked up well with Santi Cazorla as Swansea were pushed back.
But the home side grew into the game and, while Arsenal lacked a final ball, Swansea's more prosaic approach - get the ball wide, get in a cross - paid dividends. Bacary Sagna dived to head away the best of those deliveries from Dwight Tiendalli.
The first clear-cut chance arrived in the 13th minute. Graham, shouldering an extra burden in the absence of Michu, outmuscled Mertesacker and fired in a shot that was brilliantly pushed away by Wojciech Szczesny.
Arsenal responded and Walcott was the instigator, producing two runs through the middle to open up the Swansea defence. In the 20th minute one surge ended with a pass to Giroud and he wisely cut the ball back for Ramsey to feed Walcott, but his shot was blocked.
Then Ramsey, impressive on his return to Wales, drifted past two markers inside the box only to be denied by Ben Davies as he shaped to shoot from close range. Cazorla was the next to threaten, getting underneath a cut-back from Gibbs when he should really have hit the target.
But once more, having soaked up a wave of pressure, Swansea went incredibly close to scoring. This time it was Bartley who so nearly wrote himself a dream script against his former club, climbing above Mertesacker to power a header against the crossbar.
That was a warning sign for Arsenal but, to their credit, they raised their game after the restart. Giroud, quiet before the break, scuffed one shot wide but connected well with a first-time effort from Walcott's pass, only to see Vorm save with his legs.
Vorm denied Giroud again when he met Wilshere's cross on the volley, and Ramsey tumbled in the box after a collision with Tiendalli. Nothing was given.
Arsenal were piling on the pressure and a goal looked on the cards - but it came at the other end.
Michu had entered the fray in the 57th minute. In the 58th his first contribution was to break the deadlock. It was a soft goal from Arsenal's perspective, Michu getting the better of Mertesacker and powering clear of Mikel Arteta and Sagna before rolling the ball past Szczesny.
Now Arsenal had to respond. Giroud should have delivered an equaliser within minutes but could only divert Ramsey's excellent cross wide of Vorm's post.
Ramsey was replaced by Podolski but, as time ticked on, it looked like one of those days for the visitors. Walcott got in behind the Swansea defence but shot wide and Podolski slid a shot wide from close range.
The German made amends with nine minutes left, turning sharply to sweep home a powerful low shot after Sagna and Koscielny had done well to keep an Arsenal attack alive.
And the comeback seemed complete two minutes later when Gibbs - not known for his goals - brilliantly volleyed Giroud's lofted pass into the roof of the net.
With Arsenal on top it looked like the job was done. But Graham had other ideas, making the most of poor marking in the Arsenal box to sweep home with four minutes left following a Swansea corner.
Koscielny could have won it as the tie entered stoppage time but the outstanding Vorm pushed his header away and then watched the Frenchman volley the rebound over the bar.
But Swansea had a good late chance too, Tiendalli finding the side-netting with Szczesny well beaten.
This was probably more a missed opportunity than a fair result. But Arsenal are still in the cup - and that's what matters.
- Gibbs Goal! Yellow Card
- Ramsey 73 Yellow Card
- Podolski 73 Goal!
- Andre Santos
- Bartley Yellow Card
- Britton (C) 69
- Routledge 56
- de Guzman 56
- Graham Goal!
- Hernandez 56
- Michu 56 Goal!
- Agustien 69