Ireland vs. Scotland: 3 Key Battles That Will Shape 2016 RBS 6 Nations Clash

Dethroned champions Ireland will play host to Scotland in the final round of the 2016 RBS Six Nations on Saturday, with each hoping they can maintain a strong finish to proceedings.

Both sides emerged triumphant on Matchday 4, and while Ireland ran away with a 58-15 demolition of Italy, Scotland's tournament received a major boost thanks to their 29-18 win against France.

Neither team can win the title, but there's still a lot to play for in Dublin, as the winner has the chance to finish as high as second. The loser could drop as low as fifth come the end of the competition.

Read on as we profile the biggest head-to-head battles set to decide Saturday's Aviva Stadium showdown, with Ireland set to name an unchanged XV from the team that defeated Italy last time out.

1. Johnny Sexton vs. Duncan Weir

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Scotland have suffered a considerable casualty after Scottish Rugby announced Duncan Weir will stand in for regular fly-half Finn Russell on Saturday after the latter went down early against France with a head injury.

Weir will find himself falling under the cosh, too, as he prepares to face Johnny Sexton, who, despite Ireland's woes for the great majority of this Six Nations, has often been the bright spark in his back line.

He and half-back partner Conor Murray have maintained high standards while those around them have not. Russell and Scotland team-mate Greig Laidlaw have played a similarly essential role for the Scots.

There was talk Sexton was off the boil and struggling with injuries prior to the Six Nations, but winger Andrew Trimble recently hailed the fly-half's ability to shrug off such doubts, per Murray Kinsella of The42:

"

I’m tempted to say Johnny wants to prove people wrong, but I don’t think Johnny really cares that much. I don’t think Johnny would buy into any of that.

He just plays the type of rugby he wants to play. He just wants to perform as well as he can. He takes on a lot of responsibility for our team performance, our shape, our pattern, our tempo, everything, and he takes the credit when it’s going well and the flak when it’s not going well.

"

The major factor separating these two 10s is experience, and that difference may show in Weir's decision-making, just lacking the sense of calm Sexton so consistently exudes.

Neither playmaker is afraid of taking it to the line, and with two such talented midfield setups also set to collide, the platform Sexton and Weir lay on for their centres will also be of critical importance.

2. Tommy O'Donnell vs. John Hardie

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The injury-enforced absence of Sean O'Brien has been a terrific blow to the Ireland squad and confidence as a whole, and emerging youngster Josh van der Flier followed the Tullow Tank onto the treatment table this week.

That absence has paved the way for Tommy O'Donnell to make his way back into the Ireland XV, after coach Joe Schmidt was quoted by Irish Rugby, where he said Van der Flier had "shipped a few bumps" ahead of the Scotland match.

O'Donnell's upcoming openside opponent, John Hardie, managed a major feat in Scotland's victory over France last Saturday by notching a match-high 13 tackles, under-pinning his place as an increasingly vital cog for his adopted nation.

Munster coach Denis Leamy has rightly stated this is the first Scotland team in years that genuinely has the quality to hurt Ireland, and he highlighted the fact a big game is needed from the Ireland back row, per The42:

"

The Irish back-row will be up against it, that’s not something that will phase them but there will be big games needed from CJ [Stander], Jamie [Heaslip] and Josh. They’ll need to do what they did [against Italy] and probably bring a little bit more as well.

This will be a different test. I’ve been very impressed with CJ and Josh, they’re both new to international rugby and they’ve both taken very well to that standard and level.

"

While Van der Flier won't line up as expected, the return of a fit-again O'Donnell is by no means a hindrance to this Irish team, with the Cahir man ready to offer a similarly energetic presence at openside.

He will also be expected to match Hardie in the turnover count considering Scotland stripped France of possession a massive 13 times on Sunday, allowing their possession to take grip of the clash.

The pressure is on O'Donnell to ensure his backs don't get caught in situations isolated enough to be taken advantage of in such a manner.

There's also a risk of O'Donnell being caught cold after a month out of action, during which time Hardie has excelled under Scotland coach and New Zealand compatriot Vern Cotter.

3. Simon Zebo vs. Stuart Hogg

Rob Kearney's hamstring woes may have kept the full-back from his usual spot in the Ireland XV this year, but the evolution of Simon Zebo as a stand-in 15 has continued in encouraging fashion.

Some might even tip the Munster man to keep his place ahead of Kearney when the latter returns to fitness, so impressive have his performances in the No. 15 jersey been thus far.

But Scotland's Stuart Hogg is a different kettle of fish, and Zebo has a task on his hands on Saturday that will push him to the brink in all regards—be it the aerial duel or ensuring his line of defence stands resolute.

Hogg's dazzling feet were on full display against France, as he finished off a patiently built try in Edinburgh. Zebo beat more defenders than any other Irish player (four) despite failing to score against Italy. 

One thing Zebo possesses that Kearney often does not is that sprinkle of magic, that air of arrogance that makes him attempt the incredible; sometimes it comes off to great effect, and other times it doesn't.

The most enticing thing about Saturday's duel is that Hogg boasts that same quality and has shown it on numerous occasions already in this tournament, making for a promising head-to-head at full-back.

The high ball will be a testing battleground for both players as Zebo looks to showcase the same safe pair of mitts Kearney usually does. Both stars also bring incredible carrying threats into their lines.

All statistics come courtesy of ESPN Scrum.