A team featuring Lionel Messi can never be ignored, even though the 2014 runner-up barely made it to this World Cup.
But other key talents like Sergio Aguero and Gonzalo Higuain have been far from being in top form for Argentina. That is why little-known Boca Juniors striker Daria Benedetto has been deployed up front.
KEY PLAYER: Messi (Barcelona) — Doubted by fans, yet the five-time world player of the year delivered. Argentina would not be going to Russia without his goals and leadership. Turns 31 during a tournament that could yet crown his career.
COACH: Jorge Sampaoli — The 57-year-old Argentine is his country’s third coach in less than a year. His team has not impressed so far, with only one win in four official matches. His team is the biggest question mark in the World Cup.
With just 330,000 people, Iceland is the smallest country ever at the World Cup.
The city of Moscow alone outnumbers Iceland’s entire population 40 times over, but this is a team of giant-killers.
Last year’s run to the Euro 2016 quarterfinals, knocking out England on a memorable night in Nice, showed the talent and determination in Iceland’s team. Qualifying for the World Cup ahead of Croatia and Ukraine proved last year wasn’t a one-off.
Expecting more success in Russia might be optimistic, but with Iceland’s passionate fans and their “thunderclap” chant, nothing can be ruled out.
KEY PLAYER: Aron Gunnarsson (Cardiff City) — Gylfi Sigurdsson may be the main attacking threat, but bearded captain Gunnarsson inspires a gritty team.
COACH: Heimir Hallgrimsson — Not many teams are coached by a dentist, but Iceland isn’t most teams. Took sole charge after co-coach Lars Lagerback left last year.
Croatia had to squeeze through the playoffs for the second straight World Cup despite having at its disposal a generation of players capable of making the difference. Led by playmaker Luka Modric alongside Mario Mandzukic, Ivan Rakitic and Ivan Perisic, Croatia is on paper a tough team to beat.
It needs the players to replicate their club form on the international stage at a major tournament.
KEY PLAYER: Modric (Real Madrid) — Croatia looks at Modric, its undisputable leader in hopes to emulate the third-place finish at the 1998 World Cup.
COACH: Zlatko Dalic — Took charge of a critical situation with one game remaining in the qualifying. Presided over a victory over Ukraine 2-0, then Croatia overcame Greece in the playoffs.
The first team from Africa to qualify, and convincingly.
Won a group that contained current African champion Cameroon, former champion Zambia, and Algeria. A 4-0 victory over Cameroon 4-0 emphasized when they get it right the Super Eagles can be a handful for any side. Argentina found that out in November when Nigeria came back from 2-0 down to win their friendly game in Russia 4-2.
Nigeria has qualified for five of the last six World Cups.
KEY PLAYER: John Obi Mikel (Tianjin Teda, China) — While Nigeria has attacking talent aplenty with Alex Iwobi, Kelechi Iheanacho and Victor Moses, captain Mikel has provided crucial stability in central midfield.
COACH: Gernot Rohr — Like Mikel, Rohr has been a calming influence for Nigeria, which has changed coaches eight times since the last World Cup in Brazil.