Group B has a massive clash early on as Spain take on Euro 2016 winners Portugal.
Can Cristiano Ronaldo get his side off to the perfect start? How will Spain recover from the chaos that has enveloped them already, with Julen Lopetegui sacked before a ball has been kicked?
Tom Kundert (Portugal) and Dermot Corrigan (Spain) look ahead to Friday's big match at the Fisht Olympic Stadium, Sochi.
What's at stake?
Tom Kundert: When the World Cup group draw was made back in December at the Kremlin Palace in Moscow, this match immediately stood out. A clash between the Iberian neighbours -- one many peoples' favourites and the other boasting the world's most high-profile footballer -- was always going to be a mouth-watering occasion.
A remarkable sequence of events in the lead-up to the match has only heightened expectations. First, four of Portugal's squad members unilaterally rescinded their club contracts at Sporting Lisbon. Not to be outdone, Spain sensationally sacked their coach Lopetegui TWO days before the match.
If the off-pitch chaos is mirrored on the field, we could be in for something highly entertaining.
Dermot Corrigan: Following all the drama of the last few days, Spain's entire tournament now rests on how they do in their opening game.
The sacking of national manager Lopetegui, hours after Real Madrid announced him as their new club coach, has left everyone in and around the La Roja camp reeling.
Quickly appointed Fernando Hierro must get his players' minds focused on just playing this 90 minutes -- as a defeat in the Group B opener would surely just lead to more recriminations and turmoil both inside and outside the squad.
TK: William/Moutinho vs. Iniesta/Isco
Spain have got their swagger back. The team that dominated international football from 2008-12 with a very particular style is again swatting aside all-comers. Their ability to dominate possession and scythe through the middle of the opposition defence with intricate passing is at the root of their success.
It is therefore excellent news for Portugal that William Carvalho and Joao Moutinho at the base of Portugal's midfield have hit a rich vein of form and formed a great partnership in the pre-tournament friendly matches. If the duo can limit the influence of Andres Iniesta and Isco, Portugal have every chance of getting a positive result.
DC: Ronaldo vs. Ramos
National captains Cristiano Ronaldo and Sergio Ramos will come into close contact over the 90 minutes -- with Real Madrid's two alpha-males sure to want to come out on top.
Ronaldo has never scored in four meetings against La Roja, and suffered two of his biggest career disappointments, at the World Cup in 2010 and Euro 2012, against the country where he plays his club football.
Ramos is unlikely to shackle his trademark physical approach, even against his long-time teammate. And if he and Gerard Pique can keep Portugal's talisman quiet, Spain will be very happy indeed.
TK: Goncalo Guedes
Star performances at Benfica earned Guedes a big-money move to Paris Saint-Germain, where he did not get a look-in for six months and it appeared another case of a promising youngster biting off more than he could chew. A season on loan to Valencia, however, worked out extremely well, with a series of exhilarating displays of pace, directness, strength and end-product.
For Portugal, coach Fernando Santos has been used him as a central striker rather than his Valencia role as a winger or wide midfielder, and he has looked equally devastating, scoring two excellent goals in the final pre-tournament friendly against Algeria last week. Can he repeat the trick against Spain? He won't be afraid of La Liga defenders, that's for sure.
DC: David Silva
It is still uncertain who will start up front for Spain, with Iago Aspas' recent performances perhaps edging out Diego Costa and Rodrigo Moreno.
But Spain's most reliable source of goals over the last two years has been Manchester City midfielder David Silva -- who has contributed a tremendously impressive 11 goals and six assists in his last 18 internationals.
Likely to roam from a starting position on the right and link inside with Iniesta, Silva has shown an outstanding ability to be in the right place at the right time to finish off team moves.
TK: Diego Costa
Costa is a horrible striker for any defender to face. He will certainly do everything -- within the rules of the games or outside them -- to unsettle Portugal's back four. Portugal's World Cup 2014 campaign was derailed almost before it started when Pepe lost his rag against Germany and got sent off in the first half of a disastrous 4-0 opening defeat. Should the two players, both born in Brazil, do battle in Sochi on Friday, Portugal fans will be praying their key defender comes out on top.
DC: Goncalo Guedes
While Ronaldo will be closely marked, Spain possibly fear Portugal winger Guedes even more at this point.
Guedes was outstanding on loan at Valencia from Paris Saint-Germain last season, scoring six goals and giving 11 assists, and impressing especially in big games against Madrid and Barcelona. Spain's defence is also often vulnerable to quick counter-attacks, which is Guedes' speciality.
The more naturally defensive Nacho Fernandez may therefore get the nod over youngster Alvaro Odriozola at right-back, with first choice Dani Carvajal not yet 100 percent fit.
TK: 1-1. Both teams started World Cup 2014 with disastrous defeats and never recovered. They will be desperate to avoid another opening day loss.
DC: Spain 1-0 Portugal. It will be tight and tactical, but Spain to nick it with a late goal.