Published Monday, 26 May 2014
O'Neill was left to rue missed chances. (© PA)
The visitors took the lead after 17 minutes at the Aviva Stadium when Ahmet Ilhan Ozek headed home, before substitute Osman Tarik Camdal doubled their lead in the second half.
Jon Walters' late strike prompted a fightback by the Irish but they were unable to equalise and slumped to a second successive friendly defeat on home soil after March's loss to Serbia.
It left O'Neill to rue a string of missed chances and two penalties which weren't awarded in a game he felt the Republic could have won.
The Ulsterman said: "I actually thought that we created a lot of chances in the game and I genuinely don't know how we lost the match. A combination of things - probably poor finishing, some great saves by the goalkeeper too - but we should have had the game out of sight by half-time.
"I thought we played really well. I was just saying in the dressing room, there are big moments in matches where you have to really defend stoutly.
"Eventually we conceded two goals tonight when I think that there should have been less danger.
"That said, genuinely going forward, I thought we were excellent and somebody is going to earn themselves a fortune by being able to put the ball in the net, an absolute fortune."
One player who impressed O'Neill was playmaker Wes Hoolahan.
The manager continued: "I thought little Hoolahan played brilliantly for us. He tried to create things for us during the course of the game.
"Sometimes some big boots come in and shove him off the ball a little bit, but overall he showed a great determination and great ability to try to manoeuvre it.
"He was excellent for us."
© UTV News