Northern Ireland manager Michael O'Neill has hailed Cristiano Ronaldo as a "goal machine" ahead of tonight's World Cup qualifier against Portugal.

When Ronaldo steps out at the Dragao Stadium he will, at the age of only 27, become only the third Portuguese player to win 100 caps after Luis Figo and Fernando Couto.

After an unstoppable start to the season with Real Madrid, few would bet against him marking the occasion with a goal, or more, but O'Neill has been preparing his side for a week to play the role of spoilsports in Porto.

"We have to recognise the quality of the opposition but we are not sitting here just hoping for Ronaldo to have an off night, we have trained to this level in preparation," O'Neill said.

"It is our job to make sure they do have an off night and we can add to them having a frustrating night by taking our opportunity when it presents itself.

"We know what we are facing here. I think what Ronaldo has is he is a goal machine as well as creative, I have seen him numerous times, we know where the threat will come from.

"His ability is not just in set-pieces or taking free-kicks but also corners and he is very good in the air, attacking things from the back post area.

"That is all stuff we have worked on. Can we reduce his possession? Can we get men around him to make life difficult? Of course.

"I would be happy if he has a really poor game and he is remembered for having a bad night on his 100th cap."

"I would be happy if he has a really poor game and he is remembered for having a bad night" - Michael O'Neill

Northern Ireland captain Steven Davis, meanwhile, is eager to make up for what was widely accepted to be an opportunity lost last month.

Defeat away to Russia in the Group F opener was always likely, but a 1-1 home draw to Luxembourg left a sour taste in the mouth and Davis wants to banish that disappointment at the first opportunity.

"Luxembourg was a big chance to get three points and we were massively disappointed not to, so hopefully something special can happen here and that will kick us off for the campaign," he said.

"I think everyone was disappointed after Luxembourg. It was a frustrated dressing room after the game, so this gives us an opportunity to put something right.

"It's not easy, but we are definitely due a good result."

Portugal manager Paulo Bento took the opportunity to steer some of the pre-match attention away from Ronaldo yesterday, saying his star man needed to remember his responsibilities to the team.

"I do not expect anything different from him because of the fact that he is getting his 100th cap," he said.

"What I expect from him is to integrate into the structure we have got and to show all of his ability and quality in the match."