Republic of Ireland captain Nathan Collins said he "doesn't know" why Cristiano Ronaldo celebrated Ruben Neves' late winner for Portugal in front of Jake O'Brien's face when the teams met in October.

Ronaldo had a penalty saved by Caoimhin Kelleher in the game in Lisbon, before Neves scored a 91st-minute header to hand Roberto Martinez's side a 1-0 World Cup qualifying win over the Irish.

Reflecting on defeat game before Portugal's visit to Dublin's Aviva Stadium on Thursday, Collins cited irritation at his own performance as the possible reason for the 40-year-old's excessive celebration in front of O'Brien.

"I guess he was frustrated that he didn't score himself potentially, I didn't see it. I only saw it afterwards," said the Brentford defender.

"I didn't really understand why, I don't know.

"In the game, I'm not thinking about wrecking their heads or being this, that and everything. You just get on with the game."

'We must create horrible situations for Portugal'

The Republic of Ireland come into their penultimate World Cup qualifier in Dublin with their hopes of reaching next year's tournament in the balance.

Heimir Hallgrimsson's side sit third in Group F, six points behind Portugal and one behind Hungary.

They need a result against Portugal to take their chances of securing second place and a play-off down to the final day against Hungary.

Collins hopes they can take confidence from their performance in Lisbon and that, with a sizeable Aviva crowd behind them, they can cause a shock.

"I think not many teams want to come to the Aviva and go, 'we're really up for this, we really want to fight for this'," he said.

"That's where we gain our motivation, that teams are looking at us and going, 'ah, not Ireland away'.

"I think that builds confidence, it builds motivation and you just have to bring it on to the pitch then. You want to create that kind of fortress at home and make it tough for teams coming here."

To get Irish supporters onside, Collins acknowledged they must deliver a more front-foot display than their previous home game, a narrow 1-0 win over 10-man Armenia.

"It's what we do on the pitch, winning your duels, winning your battles, playing forward passes, getting in behind them, creating horrible situations for the opposing team," he said.

"Once we do that, I think the fans back us even more." (BBC)