Ireland's World Cup qualifier with Denmark was finely poised heading into the second leg in Dublin this evening after a 0-0 draw in the first match.
Eriksen then stole the show, putting the visitors ahead in the 32nd minute, and scoring two more after the break.
The midfield maestro, who had missed a couple of decent chances in the goalless playoff first leg, made no mistake in the Dublin return as his treble put the Irish to the sword.
It was Denmark who got the next goal as Eriksen found the back of the net with a composed finish to complete his hat-trick.
It'll be the 5th World Cup appearance for Denmark, last playing in 2010, not making it out of the group stage. "They are technically better than us and had a world-class player [Eriksen] in their team". "We were well beaten in the end after a good start".
"It's a insane feeling right now, we've been fighting together for so long", Eriksen said.
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More poor play from Ward then set up Eriksen who blasted home his third goal of the game. "We obviously got off to a great start and perhaps James second goal (had he scored) might have made a big difference in the game", he said.
"We highlighted Eriksen as the key player on Saturday and we sang the praises of the staff and players for marshalling him and to witness what we just seen here beggar's belief", he added.
Sub Shane Long threatened to get one back for the Boys in Green but there was still time for none other than Nicolas Bendtner to rub salt into the gaping Irish wound, converting a spot-kick after the ex-Arsenal man had been felled in the box by McClean.
"'Thank you very much for giving us space', because they locked us down in the first leg very well and Eriksen was out of the game, and today he was fantastic."
"We'll take this with us and try to score as many goals as possible at the World Cup as well", said the midfielder, who doused former worldwide defender Lars Jacobsen, who was broadcasting for Danish TV, with champagne as he celebrated.
Former Leicester and Celtic manager O'Neill's defensive style of play has often been criticised and his side scored three or more goals in a single game just once in their 12 qualifying and play-off matches.