Neymar felt the effects of the Swiss strategy long after the match ended, limping out of training on Wednesday as he continues to recover from a foot injury he picked up before the tournament. He trained on Thursday and was confirmed as a starter for the match against Costa Rica overnight.
Superstar Lionel Messi also faced heavy marking but had two uninspired performances for Argentina, now on the verge of elimination after a 3-0 defeat against Croatia.
Throughout the matches against Iceland and Croatia, disciplined defenders and midfielders stopped Messi from making his famous runs and getting one-on-one chances.
Against Iceland, Messi saw his penalty kick saved by goalkeeper Hannes Halldorsson, and the game ended 1-1.
Against Croatia, he crumbled with the rest of the team, which now must beat Nigeria in their final group game to have any chance of advancing to the next phase.
"Messi is human," Aguero said after the Iceland match. "Sometimes things happen for a reason. We need to be with him. This was a bad day, but he can decide a match at any given moment. Hope he is better against Croatia."
Croatia was taking note.
"You can't stop him with one player, you have to defend like a team. You saw that with Iceland," said defender Dejan Lovren.
Egypt striker Mohamed Salah set an English Premier League scoring record for Liverpool and held all the hopes for a deep run by the Pharaohs in their return to the World Cup, until he injured his shoulder playing for Liverpool in the Champions League final in a clash with Real Madrid's Sergio Ramos, of Spain.
Salah sat out the opening 1-0 loss to Uruguay in Yekaterinburg, with coach Hector Cuper hoping to have him fit for Egypt's second match, against Russia.
He made his World Cup debut in St Petersburg and scored from the penalty spot but only after the hosts led by three goals and his mobility was clearly affected. He barely touched the ball in the first half and avoided physical contact with Russian defenders the entire game, and Egypt were eliminated with a match to play.
Ronaldo isn't entirely alone in starting strongly. Diego Costa has three of Spain's four goals, while Harry Kane has both of England's goals.
Luka Modric scored one goal and set up the other in Croatia's 2-0 win over Nigeria, and clinched victory with his side's second goal against Argentina yesterday.
And there's plenty of time for others to turn things around. Kylian Mbappe, the 19-year-old striker at the centre of the second-most expensive transfer in history, managed just one chance in France's 2-1 win over Australia in Kazan but scored against Peru into an empty net. His famous runs and dribbles, however, were blocked by Australia's physical game.
It's early and the tournament has seen plenty of stellar play from lesser-known players but many of the star scorers have work to do.
- AP