"This is as difficult a place as there is to come. We are disappointed to only come away with a point," O'Neill said.
"Credit the players, their desire and workrate was magnificent," he added.
"The togetherness and spirit in the squad is unquestionable. The boys all worked for each other and we soaked up the pressure well.
"Our shape was fantastic and the way we went about our job was fantastic, I thought the players maybe deserved more.
Northern Ireland Northern Ireland goalscorer Niall McGinn is delighted to score his first international goal as Michael O'Neill's team earn an unexpected 1-1 draw against Portugal in the World Cup qualifier
"This result will give us great confidence for the future and there is a lot more to come from this team if we continue to improve and grow."
Niall McGinn, scorer of the goal that took Northern Ireland to within 11 minutes of a famous victory, admitted it had been an incredible night.
"This is a dream come true and I'm delighted to have scored my first international goal," McGinn said.
"I just saw the keeper coming and dinked it over him. The boys were great, especially in the first half, and we can hold our heads high after this result."
Aaron Hughes, the Fulham defender, said the squad had known they had "nothing to lose" against the Euro 2012 semi-finalists for whom Cristiano Ronaldo won a 100th cap. "We kept our shape, defended well, and everyone helped each other out," he said.
"Portugal were very fluent up front - they had a lot of movement but we coped really well. All the lads put in a great shift."
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