All eyes will be on hosts Russia as they tackle Saudi Arabia in Moscow on June 10 in the first action of the 2018 World Cup.

Monday marks 100 days to go until it is time for the great and the good to tread the boards on football's grandest stage. Experience tells us there are plenty of twists and turns to come before the big kick-off.

From a superstar in a race against time to be fit, to selection dilemmas for coaches and officials being under pressure like never before, we look at some of the major issues on the agenda as the countdown to Russia 2018 reaches its final stages.

Neymar on the mend

Brazil eased dominantly through the treacherous CONMEBOL qualifying section and their form under Tite means the Selecao are well placed to banish the humiliation they suffered on home turf in 2014. But their plans were thrown into flux a week ago when Neymar suffered a broken metatarsal in Paris Saint-Germain's Ligue 1 win over Marseille.

The frenzied events of the days that followed – PSG coach Unai Emery saying Neymar might avoid surgery, surgery happening after the player's father stated a preference for that route and differing recovery timeframes stated by the respective club and national-team setups – gave a taste of the saga to come as one of the world's wealthiest clubs and most iconic footballing nation fret over the wellbeing of their prized asset. Brazil's tournament opener against Switzerland on June 17 looms large.

So near and yet so VAR

The International Football Association Board (IFAB)'s unanimous approval of video assistant referees (VAR) means the much-debated technology is set to be used in Russia, with a final decision to be made by FIFA on March 16. Ever since it was trialled at the Confederations Cup last year, world football's governing body have spoken enthusiastically about VAR as a giant leap forward in terms of just and fair decisions, but similar support is hard to find elsewhere.

The "game's gone" wing of supporters have been volubly resistant, as is their wont, but even advocates have been alarmed by the often confused and clunky implementation across major matches in Germany, Italy, Australia and England. According to IFAB figures, VAR has increased the accuracy of reviewed decisions by 93% to 98.9% - a return that makes a new and flawed system worth persevering with. Nevertheless, the chance of all the kinks being ironed out by the World Cup is somewhere closer to the other end of the percentage scale, meaning the whole VAR project might be dealt irreparable damage in Russia.

Argentina stars scrap for places

Lionel Messi is certain to provide numerous headaches for opposition defences at the World Cup but at the moment he presents a problem for Argentina's enviable batch of world-class forwards. Put simply, there are only so many of them Jorge Sampaoli can pick alongside Messi. The former Chile and Sevilla boss brought Gonzalo Higuain in from the cold for his squad to contest forthcoming friendlies against Italy and Spain but left Paulo Dybala and Mauro Icardi on the outside looking in.

Sergio Aguero was also dropped earlier this season, although a rich vein of form for a dominant Manchester City means Messi's great mate has probably already done enough. Additionally, Sampaoli has not entirely ruled out a recall for Carlos Tevez, who is back among the goals at Boca Juniors. Serie A stars Dybala, Higuain and Icardi face a high-pressure end to the campaign, while the need to get the balance absolutely right for Messi's final World Cup tilt of his peak years should weigh heavily upon Sampaoli.

Who is England's number one?

Not knowing who your first-choice goalkeeper heading into a World Cup is a recipe for calamity, as then England boss Fabio Capello can vouch for after his South Africa 2010 experience. In defence of the man currently occupying Capello's old role, it is tricky to see how Gareth Southgate could know with any certainty who will don the gloves when the Three Lions face Tunisia on June 18. Instead of rebuilding from painfully being found surplus to requirements at Manchester City, Joe Hart has been consumed within his own rubble and is unlikely to play for West Ham again this season.

Opportunity knocks then, but the cast of hopefuls might let it trickle into the bottom corner on current form. Jack Butland's error-strewn efforts have compounded Stoke City's relegation troubles in the Premier League, while Fraser Forster is similarly complicit in Southampton being at the wrong end of the table. Tom Heaton might have been a frontrunner before injury destroyed his campaign at Burnley, where uncapped understudy Nick Pope looks as good a bet as any to challenge the unquestionably talented Jordan Pickford, who has mixed peaks with troughs since joining Everton.

Plenty to ponder for France

Defeat at the final hurdle before their adoring public was a bitter blow for France at Euro 2016, although the sight of sublime talents flowering everywhere you looked in 2016-17 took the edge off for Didier Deschamps. The current campaign has not been as kind to Les Bleus' stars and Deschamps will have egos to stroke and confidence to mend once he selects his final 23. Kylian Mbappe is sidelined at PSG with a sprained ankle – an ailment that pales next to the hamstring woes that have decimated Ousmane Dembele's first season at Barcelona.

Tiemoue Bakayoko's fitness failed him at Chelsea long after his form, with Alexandre Lacazette's struggles since joining Arsenal following a similar trajectory. Bakayoko's former Monaco team-mate Benjamin Mendy has spent six months out with cruciate knee ligament damage. Paul Pogba would ideally be credited for a Manchester United win rather than blamed for a poor showing sometime soon, while the Premier League starts Olivier Giroud left Arsenal in search of at Chelsea need to materialise. France's well of talent is arguably deeper than any other nation but Deschamps cannot be pleased by the nature of his selection headaches.