John O'Shea's Republic of Ireland face a huge return leg against Denmark after drawing 0-0 in Copenhagen on Saturday evening.
O'Shea and Sunderland team-mate Aiden McGeady were unused substitutes as Martin O'Neill's side earned a draw in the World Cup qualifying play-offs.
The second leg is in Dublin on Tuesday night, with the winner advancing to next summer's finals in Russia.
"It was a tough evening and the players did splendidly," O'Neill told the BBC.
"We've come out the other side and it's all to play for. We'll have to win a game and we might have to score a couple because Denmark are capable of scoring."
Meanwhile Paddy McNair and Northern Ireland will have to overturn a 1-0 deficit in Switzerland tonight following defeat in Belfast last Thursday.
Youngster Elliot Embleton was also on duty on Saturday, coming off the bench for the final minutes of England U19s' 2-1 win over Iceland in Bulgaria.