Paul Osam's side need to win their final match of the tournament and hope Northern Ireland fail to win against Wales to claim their third successive Victory Shield title.
After an impressive campaign for Bohemians in the SSE Airtricity National U15 League, O'Brien was named as captain for the tournament in Tralee, Kerry.
The former St. Kevin's Boys man hopes to cap off a memorable week by lifting the Victory Shield and has spoke of his immense pride playing for Ireland.
"It has been unbelievable. Playing for Ireland is incredible for me, my family and my club as well. It's the best thing I've done in my life," said O'Brien.
"It was a great performance against Wales and we deserved the win. We didn't do ourselves justice in the first match against Northern Ireland, we knew we should have played better.
"We've got to take the performance from yesterday into tomorrow's game and hope the other result goes our way. We've got to concentrate on our own performance and we're looking forward to it."
Goals from Oliver O'Neill (2), Louie Barry and Andrew Moran secured a 4-0 win over Wales for Ireland before 10-men Northern Ireland fought back to secure a 1-1 draw against Scotland in the second round of fixtures.
O'Brien was an integral part of Bohemians' U15 squad this campaign and he says he thoroughly enjoyed his first season in the SSE Airtricity National U15 League.
"I've definitely improved during the season. You're playing the best players every week and it was great for me," O'Brien continued.
"I had a few injuries and my attitude dropped with it but I came through it and I'm definitely better for it. To get selected for the national team after the season is incredible.
"It's been a great year for me, playing for Bohemians and Ireland, but I've got to keep going and look to progress every year."