Heimir Hallgrimsson insisted that the Republic of Ireland do not need to change the approach they adopted in their previous World Cup qualifier against Portugal last month. 

Hallgrimsson watched on as his team were beaten 1-0 by Roberto Martinez's side at Estadio Jose Alvalade, with Ruben Neves netting a 91st-minute winner. 

It was a backs-to-the-wall display, with Portugal registering an expected goals (xG) total of 2.97 from their 30 shots, six of which were on target, to their 0.1 from their two attempts.

Cristiano Ronaldo also saw his spot-kick saved by Caoimhin Kelleher in the 75th minute, with the Brentford goalkeeper making five saves throughout that encounter. 

Ireland followed up that defeat with a 1-0 triumph over Armenia, leaving them third in Group F and one point behind Hungary with two qualifying fixtures of their campaign left. 

"Our approach is not going to change. We need to play a certain style against Portugal, whether we need a win or a draw, we need to play a certain style," Hallgrimsson said.

"We can't go all-in against a team like Portugal. It's not going to be a basketball match, and then we will take calculated risks if we need to score a goal later on in the game.

"We have a plan for it, and the players must be ready psychologically for this encounter."

A win for Portugal at Aviva Stadium will seal their place at FIFA's flagship tournament for a seventh consecutive edition, and they have been a force in qualifying. 

Indeed, Portugal have won 15 of their last 16 qualifying matches for major tournaments (Euros/World Cup), although they drew 2-2 last time out against Hungary.

Away from home, they have won their last seven by an aggregate score of 23-2, and Hallgrimsson also expects Martinez to continue with a similar playing style. 

"They probably will tweak a few things, given that they didn't create a lot of goal-scoring chances against us," Hallgrimsson continued,

"They had some shots from outside the box, some crosses, but I think we kind of controlled how they attacked us.

"We cannot defend all their threats – it's impossible – so we need to give them some areas, and then we know what to expect."

Ireland know the importance of this game, and they will be confident, having won three of their last five home matches (D2), as many as in their previous 12 (W3 D2 L7).

They are, however, looking to win consecutive home World Cup qualifiers in the same campaign for the first time since February 2009.

Just a point separates Ireland and Hungary in the group; a positive result is crucial for Hallgrimsson's side, given their rivals are in action earlier on Thursday against Armenia.

The two teams meet in their final group encounter this Sunday, and Hallgrimsson is not underplaying the significance of the test against Portugal. 

"This is probably the one that has the most riding on it, but like we've said before, we don't know how much is at stake until after the Armenian game against Hungary," he added. 

"Then we can answer that question again, about just how much importance there is to this game. It might be irrelevant, but we predict we at least need a point from this game.

"But then, of course, there's a World Cup riding on it. If that's the case, yeah, it is definitely the most important."