It's at this time of year that Helsinki begins to record a drop in the number of daylight hours as the calendar lurches towards the inescapable grip of a Baltic winter.

But through the dark, one thing will be very clear by the time the clock ticks beyond 8pm Finnish time tonight: how optimistic or otherwise Vera Pauw's Republic of Ireland can be about the hopes of reaching a first major tournament.

The mood music after an opening World Cup qualifier defeat to Sweden in Tallaght last Thursday was bullish. And so it should be given the fact that an unfortunate own goal that could easily have gone the other side of the post was all that separated those in green jerseys from the side officially ranked second in the world.

Qualification for the play-offs was not likely to decided by home and away matches against the Swedes in any case, even if a point - or more - earned from six would be the most welcome of bonuses.

Much like the last European qualification campaign when Germany were runaway favourites, the Girls in Green's focus was on trying to get the better of second seeds Ukraine whilst leaving no margin for error against the two teams further below in the shape of Greece and Montenegro.

Unfortunately on that occasion it didn't work out in Ireland's favour, with the head-to-head evenly split with a win each and the Ukrainians capitalising on two points dropped by Pauw's team in Athens.

This time, Finland are the second seed that Ireland must look to leapfrog in the race to finish behind likely group winners Sweden.

And as was vocalised by Pauw on the eve of kick-off, this evening in Helsinki is most probably "the" game.

Even before kick-off against the Swedes in Tallaght, there was always a sense that today could well set the tone for the Irish side for the remainder of the campaign.

A win over a direct rival ranked 25th in the world (Ireland are 33rd) would set down a marker, not only earning the first points of the campaign but also immediately closing to within three points of the Finns with a game in hand and with one of the two hardest away trips on the schedule out of the way.

And if we take a short detour to a parallel universe where twists, turns and sporting pitfalls are switched off and games are won or lost on paper, if Ireland were to successfully navigate all four fixtures against the two weakest teams in the group - Slovakia and Georgia - the pressure would then be on Finland come September 2022 when they are in Tallaght for the penultimate round of matches.

But no one in the Ireland camp will be getting that far ahead of themselves, especially with the fact that Finland are seeded higher and therefore are favourites on paper.

Pauw said as much while pointing out the potential pitfalls that lurk elsewhere in the shape of countries that Sweden and Finland have almost stumbled against already: "In this group there is always the danger for us and the chance for us that Slovakia and Georgia are grabbing points somewhere. So therefore this game is crucial."

While the Finns edged past Slovakia 2-1 last month, they ran out 3-0 winners in Georgia on a difficult surface to make it two wins from two and reduce their own margin for error against the bottom two seeds in the group.

Their five goals have been spread out so far with Finland's record goalscorer Linda Sallstrom opening the scoring in Georgia to net her 49th international goal making the 33-year-old striker one player that the Irish defence will have to marshal as closely as possible.

The task will be aided by the availability of Denise O'Sullivan

The two wins also marked an upturn in form for Finland, who had gone three games without a win in friendlies against Austria, Poland and Russia after sealing qualification for next year's European Championships.

All three sides are ranked above Ireland but are also below every side that Pauw's team have used as pre-World Cup qualifying preparation since the last European Championship campaign.

The value of tough tests against Denmark, Iceland, Belgium and Australia which yielded one stirring victory over the latter and four defeats is a riff oft-repeated by Pauw in the build-up to this window with the game in Helsinki regarded as the proving ground for those lessons learned.

The task will be aided by the availability of Denise O'Sullivan who emerged as an injury worry before those fears were allayed at the weekend and she was confirmed as a welcome green light for the early night conditions in Helsinki, while captain Katie McCabe has been in outstanding for club and country of late.

They will be two of the crucial headlights that Ireland will be relying on to shine brightly if the visitors are to get a result.

And the target has been set by Pauw with at least a draw sought in order to be in the "driving seat" for a play-off place.

Follow Finland v Republic of Ireland via our liveblog on RTÉ.ie/sport and the RTÉ News app and watch live on RTÉ2 and the RTÉ Player.

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