Republic of Ireland host Wales in a crucial 2018 World Cup qualifier at the Aviva Stadium in Dublin on Friday night (7.45pm kick-off).

Martin O’Neill’s side currently top Group D having won their last three matches, the latest of which an impressive 1-0 success at Austria back in November.

Wins over Georgia and Moldova have given the Irish a great chance of qualifying for their first World Cup finals since 2002, although they’ll know that they will have to be at their best against Chris Coleman’s Wales on Friday night.

The Welsh of course reached the semi-finals of the European Championships last year, beating the likes of Northern Ireland and Belgium en route to their 2-0 loss to eventual champions Portugal in the last four.

However, they seemed to have suffered a post-Euros hangover this season, as they have won just one of their four qualifying games, drawing the other three.

Coleman’s men are already four points behind Ireland heading into Friday’s clash in Dublin, and with O’Neill’s side looking to open up a healthy lead at the halfway stage of the qualification campaign, it should be a fascinating encounter at the Aviva Stadium on Friday.

So, with the build-up well underway ahead of Friday’s clash, we’ve analysed the THREE key battles which could determine the outcome in Dublin…

Ciaran Clark v Gareth Bale

Wales’ Gareth Bale has been one of the best players in the world over the last few years, and has produced some sensational performances for his country as well.

The 27-year-old has scored 26 goals in 65 games for his country since his debut back in 2006, but 2016 was without doubt his most prolific in front of goal, scoring seven goals in 11 games for Coleman’s side, three of which coming in their run to the Euro 2016 semi-finals.

He is their talisman and the one they look at to make something happen out of nothing, and Republic of Ireland’s Ciaran Clark faces the unenviable task of trying to thwart the Welshman on Friday.

The Newcastle United centre-back has done well for the Magpies this season, helping them to top spot in the Championship, and he seems to have rediscovered his confidence after a shattering season at Aston Villa last time out.

And with Bale often playing more centrally for Wales, Clark will have to be at his very best to keep the Real Madrid man quiet and ineffective.

Ultimately, if you can keep Bale quiet, you more often than not keep Wales quiet.

Thus, this is a huge battle for Ireland, and one that if they can win, they could be looking at another three points.

Jeff Hendrick v Aaron Ramsey

Wales’ Aaron Ramsey has had a frustrating season at Arsenal so far, although did miss a large chunk of the early phase of the campaign through injury.

The 26-year-old picked up a hamstring problem back in August and missed the next few months of the campaign, returning at the end of October in their 4-1 victory at Sunderland.

However, despite coming back into the side five months ago, Ramsey has still yet to find his best form, and has struggled to just seven Premier League starts this season.

Nonetheless, he is without doubt one of Wales’ best players, so his battle for midfield supremacy with Ireland’s Jeff Hendrick will be critical in determining which side comes out on top in Dublin.

The Burnley midfielder made the move to Turf Moor last summer after eight years at Derby County, and he has settled in well to the demands of Premier League football, starting 22 of their 29 league games, and scoring two goals.

He is strong and always contributes defensively, and that could stand him in good stead in trying to thwart Ramsey’s runs into the box, as well as the Welshman’s attempts to control and dominate the middle of the park.

Coming out on top of this battle will be integral to both sides in their quest for three points on Friday.

Shane Long v Ashley Williams

Southampton’s Shane Long has not been a regular in Claude Puel’s side this season, yet he is always a huge threat when on the pitch in the green of Ireland.

The 30-year-old has managed just three goals in 23 Premier League appearances this term for the Saints, although only seven of those 23 games have been starts.

Nonetheless, Long managed three goals in 12 matches for Ireland last year, and his ability to play off the last defender and chase everything down will keep Wales captain Ashley Williams on his toes in Dublin on Friday.

The 32-year-old made the move to Everton last summer after eight years at Swansea, and based on the Swans’ struggles defensively this term, it’s clear how important he was to the balance and organisation of that backline.

And he has made a solid start to life on Merseyside, starting 27 of their 29 Premier League games, and becoming the senior defender in Ronald Koeman’s rapid-improving backline.

He has excelled in either a back three or back four to underline his defensive capabilities, yet Long will pose a challenge to him on Friday, with Williams’ anticipation and positional awareness crucial to thwarting the Irishman.

Long will be confident of accelerating away from the Welshman, so Williams will know that he needs to be defensively disciplined and aware throughout if Wales are to get a result on Friday.