Major stars are expected to shine at the World Cup, and this tournament has lived up to the top billing in that respect. Here are the players who have stood out in the first week of the tournament.

1. Thomas Muller

The German midfielder has become the team's de facto False Nine, and he has looked dominant in the role. In just one game, Muller scored three goals to put himself atop the scoring race. His intelligence and tremendous technique have made him an early contender for the Golden Ball. He has now scored eight goals in just seven World Cup matches and is well on track to surpass the five he scored four years ago.

2. Arjen Robben

Through two matches, the Dutch forward has dazzled with his speed and intelligence. He undressed the Spanish defense on his own before coming up huge against Australia. He has two goals in three games; he had only two in the 2010 World Cup.

3. Robin van Persie

Not to be outdone by his teammate, the Dutch captain also has scored three goals in this tournament, including a wonderful diving header that destroyed Spain's psychological state. He will not play in the third game of this tournament, but he is slated to play beyond.

4. James Rodriguez

When it was announced that Radamel Falcao would not play for Colombia, many wondered where the goals would be coming from. His Monaco teammate, James Rodriguez, has answered that question with two goals in two games and a stunning performance leading Los Cafeteros' offense. He has been dominant and utterly resolute in his playmaking and is surely the face of Colombian soccer for years to come.

5. Guillermo Ochoa

When it was announced that "Memo" would lead Mexico in goal, there were questions about the perennial celebrity's commitment. Ochoa has proven critics wrong with the greatest goalie display in years. He made a terrific stop against Cameroon before shutting down Brazil with six huge saves, many of them unbelievable. He has undoubtedly been the best keeper in the tournament thus far.

6. Neymar

The Brazilian superstar scored two goals in the opener and carried Brazil on his shoulders alongside teammate Oscar. He was arguably better in the ensuing game against Mexico, where he created even more scoring chances but was thwarted by the aforementioned Ochoa's goalkeeping. If he continues his current form, then there is no reason to doubt Neymar's ability to win the Golden Ball the way he did during last year's Confederations Cup.

7. Oscar

Even better than Neymar in the opening game against Croatia was his teammate Oscar. The Chelsea player commanded the Brazilian offense on his own and helped his side establish its presence against a stout and resolute Croatian team. He was not nearly as effective against Mexico, but still put up a solid display.

8. Luka Modric

The Croatian star was not always at his best against Brazil in the opener, but he did have a slew of incredible moments. He was even better at destroying Cameroon's defense in Croatia's 4-0 victory. His pinpoint passing and vision proved too much for the African side.

The tournament has also featured a slew of underperforming stars who have disappointed and helped their respective sides crash and burn in the opening week. Here they are.

1. Iker Casillas

One could blame the entire Spanish team for its poor performance one week into the tournament, but a lot of that comes down to starting goalie Iker Casillas. San Iker, as he is often called, was a questionable choice heading into the tournament, and he proved his critics right. He misread a cross into the box for the third goal and made a horrific first touch to give Holland its fourth. He then flopped like a fish as he powerlessly tried to stop Robben from scoring the fifth Dutch goal. In the game against Chile, Casillas batted the ball into the center of the box off a free kick, thus assisting Chile's second goal; he could have hit it away or tried to catch it.

2. Cameroon's entire team

It is hard to single out one player for the disastrous results from the African nation thus far. Cameroon lost 1-0 against Mexico -- but should have lost 3-0. Then the team imploded against Croatia in a 4-0 whipping. it was an ugly display from the African nation.

3. Diego Costa

Back to Spain. The Atletico Madrid striker had a terrific season but was brutal for his adopted country in just two games. He had five shots on goal, but none was on target, and he seemed to stifle his team's short passing game. The Costa experiment will likely end once the tournament ends and will not be looked upon fondly.

4. Cristiano Ronaldo

The reigning Ballon d'Or winner is either injured or unable to play on the biggest stage. Ronaldo fared poorly four years ago in South Africa, and his tournament has been disastrous one game in. Portugal's 4-0 loss was not completely his fault, but Ronaldo couldn't help his team feel better about itself. This is the kind of game in which the best players try to shine through adversity. Ronaldo almost looked like he was not even trying.

5. Sergio Aguero

"Of course I can win the Golden Boot! It's there to be won." Remember those words from Sergio Aguero? One game in and that goal does not look promising. Aguero had a lot of chances to put the ball in the net and failed on each and every one. The shocking thing is how he missed them. Few were close to the target. If Argentina is to make a deep run, Aguero must be part of it. One game in, he is part of the problem.