2018 World Cup action, in Russia, enters the second week of competition as the first round of group stage matches is complete. Host Russia is in absolute control of Group A with six points in the standings and an insurmountable plus-seven goal differential. This has virtually assured that they will be advancing to the knockout stage for the first time since 1986 when Russia was part of the Soviet Union. Cristiano Ronaldo, the best player in the world, delighted with an opening game hat-trick in Portugal's highly anticipated first-round matchup against Spain [VIDEO]. Surprises abound in the first-week standings, including Iran leading Group B, Croatia leading Group D, Serbia leading Group E, and Mexico leading Group F with Swede.

El Tri's shocking 1-0 defeat over defending champion and No. 1 ranked team in the world Germany also shocked some fans.

The favorites struggle out of the gate

Brazil, the pre-tournament favorite, managed a 1-1 draw in Group E against Switzerland when they were caught playing lazily on a Swiss corner kick headed into the goal by Steven Zuber to even their match 50th-minute. Germany, second in the odds to win the tournament and ranked No. 1 in the world, lost to Mexico 1-0. Spain forced 2016 European champion Portugal to a 3-3 draw, while Argentina was tied 1-1 by Iceland, which was making their first ever World Cup appearance. England must feel fortunate for three points in the standings after they were bailed out by team captain Harry Kane's second goal of the game in the 91st-minute, securing a 2-1 victory over Tunisia.

Only Belgium, defeating 2018 World Cup newcomer Panama 3-0, performed strongly among the top 10 pre-tournament favorites.

Mexico, Japan, Senegal headline surprise winners

Mexico's shocker 1-0 over Germany [VIDEO] on Hirving Lozano's goal in the 35th-minute of its matchup is the top storyline of the tournament. El Tri showed they can play with the best in the world and can be considered a legitimate candidate to become the first CONCACAF team to reach the semifinals in World Cup history. Japan enjoyed a player advantage against Colombia thanks to the first red card of the tournament, given to Carlos Sanchez for a handball, scored on the ensuing penalty kick, and added the game-winning goal in the 73rd-minute as the Colombians unable to overcome the player disadvantage. Senegal defeated eighth-ranked Poland 2-1 on a controversial goal in the 60th-minute. The result has Group H upside down, with Senegal joining surprising Japan atop the group.

Intrigue for second round group stage play

Argentina needs a win against Group D leader Croatia.

Serbia will face the sixth-ranked Swiss, who played brilliantly against favorite Brazil, in a game where the Swiss will be looking for three points. Germany will play Sweden in what amounts to a must-win for the defending champions. Poland against Colombia in Group H will go a long way in determining who advances, with Japan and Senegal settling things earlier in the day, June 24. Will Cristiano Ronaldo continue to delight, on his way to the Golden Boot, and a strong showing by Portugal? Each passing day of competition creates new questions, with the group stage clarity coming in the following days.