Euro 2012: Players to Watch During Quarterfinal Action

You can't win the European Championship without a complete team effort, but one player's performance often makes the difference between champs and chumps.

As we've seen time and time again, matches—and sometimes entire tournaments—can be forever altered by one moment of individual brilliance.

Whether that brilliance comes in the form of a vicious strike or a perfect pass or an incredible save doesn't really matter. As long as you have one player who can make a Herculean effort in one way or another, your team has a shot to advance.

With the knockout stage of Euro 2012 beginning today, every game will have one man whose performance changes the fate of the entire match. Here are the most likely candidates to have such an impact in the quarterfinals.

Czech Republic vs. Portugal: Cristiano Ronaldo, Midfielder, Portugal

The most well-known player in this match will also be the most critical.

Ronaldo is the best footballer in Europe, an amazing athlete who can do everything on the pitch. His touch is remarkable, his strikes are often unstoppable and his speed and leaping ability cause major problems for opposing defenders.

When he's at his best, nobody in the world can stop him. Unfortunately, Ronaldo hasn't always been at his best on the international stage. He squandered several chances against Denmark, and Portugal was lucky to survive the game.

His next time out, he finally looked like the Real Madrid star we're used to seeing. He was highly aggressive against the Dutch, taking a Euro-record 12 shots and finding the net twice to lift some of the immense pressure off his shoulders.

If that Ronaldo shows up today, he will be a nightmare for the Czech back line. But if he is indecisive and fumbles his chances like against Denmark, Portugal will be on upset alert.

Germany vs. Greece: Mario Gomez, Striker, Germany

Mario Gomez was excellent in Germany's first two games, scoring all three of his team's goals against Portugal and the Netherlands. He was decisive and effective with his touches, wasting no time in putting the ball into the back of the net.

With his consecutive strong performances, it looked like his awful Champions League final for Bayern Munich was behind him. Then, he struggled against the Danes and all the doubts surrounding him came roaring back.

Gomez was wasteful with his chances, and he committed a third of his team's fouls. He will need a better game on Friday to secure his place in the starting lineup and ensure that the Germans aren't upset by the scrappy Greeks.

Spain vs. France: Fernando Torres, Striker, Spain

When Fernando Torres is confident, he's one of the five most dangerous strikers in the world. Unfortunately, his belief in himself seems to waver from match to match, which forces his play to do the same.

After squandering a few chances versus Italy, Torres rebounded beautifully against the Irish. He scored on a laser in the fourth minute, then added another goal in the 70th. It was a vintage Torres performance, straight out of his heyday from Liverpool.

However, his strong play didn't last long, as he struggled through 61 mostly ineffective minutes against Croatia.

If Torres can be cold and calculated like he was against the Irish, Spain should roll past France with ease. If he struggles, though, the tournament favorites will be in serious danger.

England vs. Italy: Mario Balotelli, Striker, Italy

I apologize for sticking with the goalscorer theme, but Italy's fate will almost certainly be decided by the volatile Mario Balotelli.

The 21-year-old Manchester City striker is insanely talented, as you can see from his amazing goal against Ireland. And, as you can see from his numerous outbursts, he might just be completely insane off the pitch as well.

Balotelli is as unpredictable as they come. He has the same remarkable ability and confidence issues as Torres, with a violent streak thrown in there just for fun.

One day, he's scoring wonder goals on one of the sport's biggest stages. The next, he's squandering easy chances with indecisiveness and making headlines in the most bizarre manner possible.

Italy faces a very tall task against England, who allowed just three goals in the group stage.

If the Italians are going to put points on the board and advance to the semis, they will need Balotelli to put on his big-boy pants and deliver a performance reflective of his talent level.