Republic of Ireland manager Heimir Hallgrimsson has said Cristiano Ronaldo makes Portugal are more attacking team due to his constant hunger to score.
The 40-year-old Al Nassr striker will head into Thursday night's Group F fixture at the Aviva Stadium with 225 caps and 143 international goals to his name, the last two of them in a 2-2 draw with Hungary in Lisbon three days after Ireland's 1-0 defeat at the same venue last month.
Ronaldo saw Caoimhín Kelleher penalty save his penalty that night, a repeat of Gavin Bazunu's feat in Faro four years earlier, but head coach Hallgrimsson is well aware of the former Manchester United star's enduring potency when the two countries face off in a World Cup qualifier.
Asked about the threat he poses, the Icelander said: "The statistics speak and answer that question. He is still scoring goals and breaking records.
"One of the reasons why they are such a unique attacking team is his desire to score goals. They will deliver crosses, they will try to find him all of the time.
"Most teams when they are winning, they would cool the game down, but Portugal want to score more goals and he is one of the reasons why this Portuguese team is a unique attacking team."
Ireland will run out at the Aviva knowing their World Cup dream is hanging by a threat after the late Rúben Neves header which cost them a precious point at the Jose Alvalade Stadium and the scratchy 1-0 home win over Armenia which followed.
They remain in third place in the group, a point behind Hungary, who would go four clear if they beat the Armenians in Yerevan earlier in the day.
That would leave Ireland needing a minimum of four points from their two remaining games -- they travel to Budapest on Sunday -- and the likelihood is a draw is the very least they need from their meeting with Roberto Martínez's men.
Hallgrimsson said: "Our approach is not going to change, so we need to play a certain style versus Portugal whether we need a win or a draw.
"We can't go all-in against a team like Portugal, it's not going to be a basketball match. Then we will take calculated risks if we need to score a goal later on in the game."
Two of the last three competitive fixtures between the sides have ended with stoppage-time winners for Portugal -- the third was a goalless draw -- and a clean sheet this time around could prove hugely significant.
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Hallgrimsson, who faces choices between Liam Scales, Dara O'Shea, Seamus Coleman and Kevin O'Toole at left-back and Adam Idah, Troy Parrott or Johnny Kenny up front, said: "Absolutely, that's our number one priority against a team like Portugal."
Ipswich defender O'Shea is likely to be key in that fight and he will draw inspiration from famous victories over the Netherlands, Germany and Italy as the nation looks for another "special" result.
O'Shea said: "This group and this team are waiting for that special result against a big team and tomorrow is an opportunity to do that.
"What an opportunity for us. Everybody is really looking forward to stepping out there tomorrow night to show what they've got and fighting for the country."