Nottingham Forest legend Martin O'Neill said he would need to have "a real think" about his future after the Republic of Ireland saw their World Cup hopes left in ruins.

Tottenham midfielder Christian Eriksen ended Ireland's play-off bid in brutal fashion with a hat-trick as the Danes raced to a 5-1 play-off second leg victory in Dublin, following the goalless draw in Copenhagen.

Republic boss O'Neill had been criticised for a perceived negative approach in the first leg, but he saw a more expansive approach cost his side dearly on Tuesday after they had taken an early lead.

He said: "I'm really disappointed, obviously, we were well beaten in the end. We got off to a really good start and had a chance maybe to make it 2-0 and we probably needed that.

"But the two goals we conceded in a couple of minutes knocked us for six."

Daryl Murphy (centre) and Denmark's Andreas Bjelland and Thomas Delaney (right) battle for the ball

O'Neill and his coaching team have verbally agreed contract extensions with the Football Association of Ireland, with their existing deals effectively expired.

But asked if the result would have any effect on his immediate future, O'Neill said: "Do you know what, I'll have to have a real think about it.

"The disappointment obviously is very, very strong tonight because we haven't been able to do it, but I have to commend the players on getting this far."

Ireland got off to the perfect start when defender Shane Duffy headed them into a sixth-minute lead, but Cyrus Christie's own goal and the first of Eriksen's treble inside three minutes turned the game on its head.

The Spurs player helped himself to two more after the break before substitute, and former Reds striker, Nicklas Bendtner sealed an emphatic win with a last-minute penalty.