Reuters/CARL RECINE
Moscow's Luzhniki Stadium will host its second game of the tournament on Sunday evening when champions Germany meet Mexico to start Group F.
Joachim Low's side are aiming to become only the third team in history to retain the World Cup, as they begin their 2018 journey at Moscow's Luzhniki Stadium.
Sweden and South Korea are the two other sides in Group F, and they will meet on Monday afternoon.
Both Germany and Mexico are tipped to emerge from this group with no real trouble, but Sunday's game may go a long way to deciding the final standings.
1. A table-topping decider?
Germany will be the obvious favourite to win this one, but Mexico will be all too aware of the potential prize on offer should they upset the odds.
With these two sides being arguably the strongest out of the four in the group, top spot may well be decided on Sunday.
Reuters/MURAD SEZER
Both the Germans and Mexicans will hope that six points from their two following fixtures should be enough to qualify but it puts extra weight on this opening game.
In the last-16, Groups E and F will cross over. With the probability of Brazil winning Group E being high, finishing second place in Group F would bring a date with Tite's side in the first knockout stage.
Sunday's fixture is important, though both sides will be careful of not losing it.
2. Can Germany set the early pace?
Die Mannschaft are unsurprisingly one of the favourites to win the 2018 World Cup, alongside France and Brazil, but can they reach the height of the bar they set in 2014?
The spine of Germany's team remains from their triumph four years ago, with Mats Hummels and Jerome Boateng forming the centre half partnership.
Reuters/LISI NIESNER
Seasoned professionals Toni Kroos and Sami Khedira are still holding down the fort in the midfield, alongside familiar face Thomas Muller. Manuel Neuer will hope to feature once more in what will probably be his final World Cup.
This Germany side has been together for some time, and with the likes of Joshua Kimmich and Timo Werner added into the mix, the side has a healthy blend of youth and experience.
Much is always expected of the holders, but can Germany set out the stool early and give Mexico the runaround?
3. Manuel Neuer or Marc-Andre ter Stegen?
Neuer's preparation for the World Cup has been hindered for some time, with his injury lay-off starting way back in April 2017.
A metatarsal fracture kept the Bayern Munich stopper sidelined until April this year, though a sheer drop and match sharpness over the year-long period forced him to spend an extra month getting up to speed.
Reuters/AXEL SCHMIDT
Neuer returned in time to be picked by Joachim Low in his World Cup side though his peers have had a thorough preparation period.
He has been handed the number 1 shirt for the tournament, but is his place safe? Low is obviously a fan of Neuer, but is sentiment getting in the way?
Ter Stegen, five years Neuer's junior, has had a comparatively stronger, more consistent season after winning La Liga comfortably with club side Barcelona. Ter Stegen has been comfortably established as the top goalkeeper at La Blaugrana for some time, though Neuer's presence has limited his chances on a more global stage.
In the two warm-up friendlies, Neuer played a full 90 minutes, but the second game against Saudi Arabia saw each play a half.
Ter Stegen has had a solid, steady season. Should Neuer, who has missed almost the entire 2017/18 season, be able to walk back into the team?
4. Mexico have a point to prove
The form of the Mexican side's regulars has been in a consistent decline for some time. El Tri have failed to make it past the last-16 of the World Cup at the last six tournaments, and given the prospect of needing to beat the champions to avoid meeting Brazil, it looks as though that trend may continue.
Long-standing members such as Giovani dos Santos, Carlos Vela, and Andres Guardardo haven't been in the best for their country, and as key members, the proof is in their recent results.
Reuters/HENRY ROMERO
Recent abject displays have forced Mexico fans into calling for the head of manager Juan Carlos Osorio, who has been at the helm since 2015.
After failing to win a game at the 2015 Copa America, followed by a 7-0 thumping by Chile in the 2016 edition, Mexico's international pedigree has come into question.
They comfortably qualified, but a poor result on Sunday will heap the pressure onto Osorio.
5. Kimmich, Werner, and Lozano
The World Cup has a habit of bringing a young starlet's name to the fore. In 2014, James Rodriguez's performances for Colombia were dazzling, and ultimately made him property too hot for AS Monaco to keep hold off.
This season, the greatest tournament on earth won't be short of young hotshots waiting to make their mark, either.
For Germany, Joshua Kimmich and Timo Werner will hope to have a World Cup to remember. At 23, Kimmich isn't the youngest player at the party, but his abilities as the right-sided fullback have seen early comparisons made to German legend, Philipp Lahm.
Reuters/THILO SCHMUELGEN
After moving to Bayern Munich in 2015, Kimmich has made the right-back position at the Allianz his own. He was selected in the final, 23-man squad for Euro 2016, and has been moving upwards ever since.
Timo Werner is the third-youngest player in the Germany squad, and at 22, has a great chance to make an early name for himself.
Euro 2016 came too early, but Werner already has eight goals in 14 appearances for the national side. Domestically, Werner is one of the hottest prospects, with 34 goals in 63 matches for Bundesliga side, RB Leipzig.
Hirving Lozano is Mexico's youngest player in Russia, and at 22, has already played in 26 matches for his country, scoring seven goals as a winger.
The PSV Eindhoven attacker is an exciting, young talent who will take over the baton from long-standing players such as Giovani dos Santos and Oribe Peralta.
Mexico's squad is aging but Lozano represents the future of the nation.
Listen to the RealSport football writers discuss Group D in Kremlins in the Basement: RealSport’s daily World Cup podcast.