If Cristiano Ronaldo is to send Portugal to the semifinals and match Michel Platini's all-time European Championship scoring record, he'll have to find a way through a Poland defence that's among the toughest of the tournament.
Ronaldo has scored eight goals from four championships, one shy of Platini's nine, though he's been on inconsistent form in Platini's home country.
Frustrated and angry in Portugal's opening draws with Iceland and Austria, Ronaldo has shown flashes of his true talent since then, scoring two goals in a 3-3 draw with Hungary and setting up Ricardo Quaresma's winner against Croatia in the round of 16.
Poland's defence looks formidable after conceding just a single goal in four games. And even that needed a stroke of genius, in the form of Xherdan Shaqiri's spectacular overhead kick for Switzerland in the last 16.
Despite a lack of well-known defenders — the first-choice centre-backs play for Torino and Legia Warsaw — the Poles have made a virtue of scraping through games, with two 1-0 wins and a victory on penalties against the Swiss. They also neutralized the attacking play of World Cup champion Germany in a 0-0 draw in the group stage.
Just like his great rival Lionel Messi, Ronaldo has never won a major title with his country. On what is widely considered the easier side of the draw, with a potential semifinal against Wales or Belgium, this could be his year.
While Portugal beat a solid Croatia team 1-0, it didn't register a single shot on target until deep into extra time. Winning ugly is fine for centre-back Jose Fonte, just as long as Portugal is winning.
"It doesn't matter if you play beautiful or ugly football," he said Monday. "You have to win and I want to win. If we have to play badly every game and win, I'll do it."
If the attack has stuttered, Portugal's defence is also a concern with four goals conceded, the joint-worst of any team in the quarterfinals, along with Iceland.
The chaotic 3-3 draw with Hungary in the last group game prompted a rethink by coach Fernando Santos, who brought in the Southampton duo of Fonte and right-back Cedric for the last 16, in place of Ricardo Carvalho and Vierinha, who had started all three group games.
Portugal also has injury concerns, as left-back Raphael Guerreiro and midfielders Jose Moutinho and Andre Gomes are all doubtful.
Poland's top scorer in qualifying, Robert Lewandowski, remains scoreless in the tournament, but he's often been a sacrificial element in Poland's strategy, keeping defences occupied to create space for winger Jakub Blaszczykowski or second striker Arkadiusz Milik. However, the resulting chances have often been wasted, especially by Milik.
As Poland bids to reach its first tournament semifinal since the 1982 World Cup, Lukasz Fabianski will continue to deputize for injured first-choice goalkeeper Wojciech Szczesny, who has missed the last three games with a thigh injury.
With files from James Ellingworth