"Torture", "pure carnage", hanging around in a stairwell watching another game and praying that someone else doesn't steal the title.

He's been through it all before and could do without the stress this time.

This weekend's Six Nations conclusion stirs memories of 2015. The similarities are indeed striking.

Nine years ago, Ireland retained the title. They did so after playing Scotland and after England faced France in the tournament closer. An identical sequence of events could unfold this weekend.

Their second championship under Joe Schmidt arrived only after a day of extraordinary drama when England threatened to snatch the trophy away from Irish hands.

Let's recap. In 2015, England led Ireland on points difference going into the final day with Wales in third. Wales' thumping 61-20 win over Italy in Rome meant that Ireland needed to beat Scotland by 21 points to top the table.

The Irish were duly up to the task and hammered Scotland 40-10 at Murrayfield. It wasn't enough to win the title on the spot, though. England faced France knowing a 26-point win would be enough, but despite building a 55-35 lead and pressing the French line, they came up agonisingly short.

'That was the mad day, wasn't it?'

When the match ended in Twickenham, there were smiling Irish eyes in Murrayfield, but only after fingernails had been obliterated during a heart-stopping conclusion to the England game.

"That was the mad day, wasn't it? Yeah, it was torture," said O'Mahony, recalling 2015.

"Wales went out and put up a big score, then we did the job and then it was pure carnage the last game.

"I'm sure it was a great watch for the rest of the world. I remember watching it from the stairwell in Murrayfield, praying to God, so, look, that's what the Super Saturday means for the competition.

"It's great that there are so many teams involved that can win it."

For Ireland, the equation is much simpler this time. They will retain the title with a win or draw against Scotland. If they lose but secure a bonus point, they are still more than likely to win the title given their vastly superior points difference.

If Ireland fail to collect a point against Scotland, they will still win the title if England fail to secure a bonus-point win over France.

For Scotland, the situation is far more complicated, and hardly one to inspire much confidence. To win the title, they need to beat Ireland with a bonus point, deny Ireland a point and overturn the points difference deficit. They then need France to beat England without a bonus point or with a bonus point by a smaller margin.

An Ireland win of any description will eliminate the possibility of 'Le Crunch' deciding the destination of the championship, and that's what O'Mahony is targeting.

"You have to discuss these things, especially the guys who are making decisions around refereeing calls, that kind of stuff, penalties," said O'Mahony of the permutations.

"We are going out to win, that's what we do for every Test match.

"Of course, there's a handful of us who might have to make a decision or need to know the permutations but we want to put in a performance tomorrow that's capable of winning."

Like in 2015, Ireland come into the final round of games on the back of a defeat. While it was Wales nine years ago, they host Scotland on Saturday a week on from being humbled by a rejuvenated England at Twickenham.

Ireland don't lose many games these days. When they do, it's significant. When the All Blacks knocked them out of the World Cup, it stopped Ireland from reaching their first semi-final and ended their 17-Test match winning run (New Zealand and England's record of 18 remained untouched).

Losing to England last week not only shattered Ireland's hopes of becoming the first Six Nations side to win back-to-back Grand Slams, it also prevented them from equalling England's record of 12 consecutive Six Nations wins.

After the All Blacks defeat, Ireland had three months of soul-searching. They have not been afforded such an extended run inside their own minds this time.

Scotland have come to wreck St Patrick's Day weekend in Dublin. Gregor Townsend's side, too, are smarting, having been stunned by Italy in Rome.

Given all the chat about a potential repeat Slam, failing to deliver the title would be a disastrous denouement for Ireland.

They will, however, be comforted by their recent track record against the Scots.

They have won their past nine meetings with the Scots dating back to 2017 and opened them up with ease during a 36-14 thumping at the World Cup, their last encounter.

With the Six Nations on the line, Ireland must use their Twickenham pain to ensure they're not huddled around a screen in the bowels of the Aviva Stadium waiting for their fate - good or bad - to be sealed.

O'Mahony, as ever, is keeping his thoughts clear and the message simple.

"You approach every game like you want to win it, which is no different this weekend for either of us," said the Munster back row, who is hunting a fifth Six Nations title with Ireland.

"Off the back of a loss for both of us, you try and focus the mind on certain things and try to make improvements and you always want your next performance to be a winning one so I'm sure we're both in the same camp in that department.

"I'm sure they [Scotland] are [more dangerous after losing to Italy] but we're in the same boat this week.

"We're certainly hurting from last week with certain aspects of the performance and losing, we don't want to lose, neither to do Scotland so we're in the same boat."