England and Italy have two of the most raucous, passionate fanbases in the world. To them, these tournaments aren't games; they're a matter of life and death.
Both countries, however, have been perennial disappointments in the past few years, which has made their strident supporters apprehensive.
Now, the pressure is on more than it ever has been, as one side will once again fall earlier than they would like to. Here are the four players under the most pressure in a European battle for the ages:
The English were able to survive and advance in the wake of Wayne Rooney's careless suspension, but now the newly coiffed striker will need to get back into midseason form.
This English side functions at a much higher level than the recent squads we've seen. There is more teamwork and less egos, which has led to a more efficient brand of soccer.
But they can't win without their star playing at his highest level.
Rooney works brilliantly up front with Manchester United teammate Danny Welbeck, and if the two can combine for a goal against the staunch Italian defense, it could put England in very good shape.
All Italian eyes will be on their capricious striker in this one, as Mario Balotelli could be the difference between advancing and staying home.
Balotelli has mixed dizzying highs (his bicycle-kick goal against Ireland) with unspeakable lows (his inexplicable botched breakaway against Spain) so far this tournament, but in the knockout round there are no more mulligans.
Super Mario is almost always the most talented player on the pitch, but if he makes a show of this match—screwing up a goal, getting a red card, etc.—the Italian fans will want his head.
John Terry has had a rough few years. It started on the field, when a missed penalty kick cost Chelsea the Champions League final. His misfortune then seeped into his personal life, where he was allegedly romantically involved with former teammate Wayne Bridge's wife. These allegations forced Fabio Capello to strip him of his national team captaincy.
It all culminated this season, when he was part of a racial controversy in the English Premier League. How Mario Balotelli—an outspoken critic of soccer's racism—will respond to that remains to be seen.
Terry is currently one of the most despised athletes in the world, but as suspect as his character might be, he has always been an incredible player. He may not be completely vindicated if he helps England advance, but he will get some of the tabloids off his back.
Gianluigi Buffon's esteemed international career seemed to have reached its apex in 2006, when he led the Italians to the World Cup title.
But since then, he has disappeared from international relevance, after an injury forced him to miss most of the team's disappointing run in the 2010 World Cup
But now he is back in the spotlight of the world's stage once again, and he has a chance to make people remember why he is one of the greatest goalies of all time.
England's attack is sure to test him, so he will need to be in rare form.