The 5 Biggest Group Stage Matches of the 2018 World Cup

Cristiano Ronaldo and Portugal will face Spain in one of the headline matches of the group stage. Which other fixtures should be at the top of your must-watch list?

With the preliminary and final squads starting to be reveled for the 32 nations attending the World Cup in Russia this summer, the picture of some of the epic clashes to come is starting to become clearer.

While the group stage has its share of innocuous matches, there are some absolute firecrackers, as well. Below are the five must see, plan ahead for, get your popcorn ready, impactful matches of the 2018 World Cup group stage.

Portugal vs. Spain

Date: June 15th

Players to Watch: Cristiano Ronaldo, Bernardo Silva, David De Gea, Diego Costa, Sergio Ramos, Thiago Alcantara

The first blockbuster match of the World Cup comes courtesy of Group B as Portugal meets Spain. Neither side should have a problem defeating the other teams in the group, Iran and Morocco, so the winner of this match would have a great chance to win the group. With Spain's victories at the 2010 World Cup and 2012 Euros, and Portugal's recent victory at the 2016 Euros, these two countries have won three of the previous four major international championships.

While Spain are behind only Germany and Brazil in terms of oddsmakers' favorites to win the tournament, their recent results at the 2014 World Cup and 2016 Euros have been horrendous. After falling in the group stages in 2014 and the Round of 16 in 2016, Spain's form has been off in the last two major events.

That's music to the ears of Cristiano Ronaldo and Portugal, who will be looking to build off their Euro victory and start their World Cup off on the right foot. On paper, Spain has the superior talent, but that was the case in the 2014 World Cup, as well, when they lost their opening match to the Netherlands by a score of 5-1.

As the fourth match that will be played in the World Cup, it doesn't get much better than this. We give Spain a 65.20% chance to beat Portugal, and our metrics peg Spain with the second-best title odds (25.12%), trailing only Brazil (38.44%).

Germany vs. Mexico

Date: June 17th

Players to Watch: Manuel Neuer, Toni Kroos, Marco Reus, Timo Werner, Chicharito Hernandez, Hirving Lozano

Germany-Mexico has the potential to be one of the most impactful matches of the entire group stage. For Mexico, a result against Germany would go a long way to securing advancement to the knockout stage. Mexico will face stiff competition from Sweden to advance from the group, and Sweden and Mexico will face Germany before meeting each other in their last game of the group stage. Going into that match, group standings and goal differential will be key, and this match against Germany will have a large impact on both of those things for Mexico.

For Germany, while anything is possible, they will almost certainly advance to the knockout stage, with our models giving them a 90.75% chance, the fourth-best odds, of getting to the Round of 16. That said, there could be a massive difference in the quality of their opponent in the Round of 16 depending on where they finish in Group F. Should they stumble against Mexico, they put themselves at risk of finishing second in the group, setting up a potential Round-of-16 matchup against Brazil.

While the memory of their last meeting against Brazil is a plea7ent 1, it would be much more advantageous to face Switzerland, Serbia, or Costa Rica instead. Germany would be wise to avoid any signs of a World Cup hangover and come out strong against Mexico on June 17th. We give Germany a 70.69% chance of topping Mexico.

Argentina vs. Croatia

Date: June 21st

Players to Watch: Lionel Messi, Paulo Dybala, Gonzalo Higuaín, Sergio Aguero, Luka Modric, Ivan Rakitic, Mario Mandzukic, Mateo Kovacic

At first glance, this match seems like an outlier compared to the others on the list. In a group with Nigeria and Iceland, both Argentia (80.34%) and Croatia (78.50%) are clear favorites to advance to the Round of 16, per our numbers.

However, the Round of 16 is where the impact of this match lies, as finishing second in the group to Croatia would set up a meeting with the winner of group C, which is very likely to be France. Winning Group D would probably result in playing one of Denmark, Peru, or Australia -- a much easier task.

Messi and company would be wise to not underestimate a Croatian side that are no strangers to the World Cup stage, having qualified for five of the last six competitions. If Argentina slip, they could find themselves facing a very difficult road through the knockout stages. Our models see this game as a very even clash. We give Argentina (34.91%) and Croatia (31.80%) very similar win odds, with a 33.29% chance of a draw.

Switzerland vs. Costa Rica

Date: June 27th

Players to Watch: Keylor Navas, Joel Campbell, Bryan Ruiz, Xherdan Shaqiri, Breel Embolo, Stephan Lichtsteiner

With several familiar sides failing to make the World Cup this year, such as Italy, Chile, and the United States, the 2018 iteration of the famed Group of Death is weaker than in past competitions. While a case could be made for Group D, Group E may have the strongest claim to the title.

With Brazil on top, Group D also boasts Switzerland (6th in the world rankings), Costa Rica (25th), and Serbia (35th). Even if Brazil sail through, this group should have drama right down to the last day, when Switzerland will play Costa Rica. Both sides made excellent runs at the 2014 World Cup, with Switzerland falling to Argentina in the Round of 16 and Costa Rica dropping out to the Netherlands on penalty kicks in the quarterfinals.

This match will almost certainly determine the fate of these two side, with one, but not both, likely to emerge from this match with a spot in the knockout stages. Our numbers have Switzerland as the favorite, forecasting them to beat Costa Rica 56.51% of the time.

England vs. Belgium

Date: June 28th

Players to Watch: Harry Kane, Raheen Sterling, Dele Alli, Jesse Lingard, Eden Hazard, Romelu Lukaku, Kevin De Bruyne

The second to last match of the group stage is arguably the most exciting one. Both Belgium and England come into Russia with young squads and high expectations. For England, that's nothing new, and neither is the disappointment that typically accompanies those expectations. For Belgium, they have had some recent success and will be looking to build on their defeat to Argentina in the quarterfinals in 2014.

In addition to the action on the pitch, this match has the potential to be an elimination match for one of these two teams. While Panama will be making their World Cup debut and are ranked 55th in the FIFA World Rankings, Tunisia are ranked 14th, only one spot behind England, so it's far from a lock that both Belgium and England advanced to the Round of 16.

If either Tunisia or Panama manage a result against Belgium or England, this match will take on a level of importance beyond determining the winner of Group G. Even without elimination on the line, this match -- which is filled with Premier League players -- should be high in action and drama and perfectly wrap up the group stage of the tournament.

Our metrics like Belgium quite a bit, giving them a 55.95% chance at beating England while the odds of a draw are 27.19%, meaning we give the Three Lions a mere 16.86% chance of winning this matchup.