Republic of Ireland boss Heimir Hallgrimsson praised a "great team performance" - but felt his side's agonising 1-0 defeat by Portugal was "painful".

Much improved from their embarrassing 2-1 defeat by Armenia in September, the Republic's dogged defending looked to have been enough to earn a crucial point, especially after Caoimhin Kelleher saved Cristiano Ronaldo's penalty.

But Ruben Neves glanced Francisco Trincao's cross home in the 91st minute to snatch a victory that moved Portugal five points clear in top spot and closer to World Cup qualification.

"I'm sharing the feelings with the players, it was painful," Hallgrimsson told RTE. "After all this work, it was not perfect, but it was a great team performance.

"We put a lot of energy into this match, defending, mostly, but we knew that we were going to need to defend and we did it quite well for most of the time.

"When we got tired, when they got on the ball, these players have the quality to find the perfect passes as you saw in the goal. We gave them too much time to run into space and to find the killer pass."

While he was content with their defensive efforts, Hallgrimsson was left to rue the Republic of Ireland's inability to threaten Portugal at the other end.

The Icelandic boss maintains, however, the positives in Lisbon outweighed the negatives as his side restored some pride following their humbling in Yerevan last month.

"We felt of course [we deserved a point] because we spent a lot of energy," he added.

"They had more chances than we did, but we had our openings and if we were cleverer on the ball, but when you waste energy defending, the decision-making when you get the chance is not perfect.

"We should be proud, not happy, but there are a lot of good things to take from it. It was a team performance; everyone did their job. There were no passengers in this game."

Republic of Ireland are still bottom of Group F with one point after three games and now face a must-win game against Armenia at home on Tuesday to keep their slim hopes of reaching next year's tournament in North America alive through a play-off spot.

Hallgrimsson hoped the diligent display will give them a boost to their belief.

"Confidence is a tricky thing, you never know what gives you confidence or takes away your confidence," he said. "We should at least be happy with the team performance.

"I'm just wary of what lies ahead of us in that [Armenia] game so now we need to shift focus and try to leave this in Portugal and be ready come Tuesday."