For the real sporting achievers among us, the purest motivation is born out of regret, a sense of time wasting away or sometimes base anger.

She came off the bench angry last Tuesday. There was also a subconscious trace of regret. The Jenny Murphys of this world bottle such emotions and harness them at the optimum moment.

“Everyone is different but getting pissed off, definitely for me, it drives me. If someone tells me I made a mistake, I won’t make the same mistake the next time,” said Murphy.

The current rugby description for what she did is beast mode.

What made her 40-minute cameo in Tuesday’s heroic, controlled dismantling of New Zealand so enjoyable was Murphy seemed to attain a new level of intensity. She kept bouncing to her feet, kept punishing opponents until her body pleaded for a break.

“Coming on, I had 40 minutes rest the others didn’t have so I should be doing extra work, I should be going into that ruck, I should be encouraging more. Empty the tank. It was good.”

Philip Doyle has used this Kildare weapon cleverly. It seemed a mistake to bench her for the USA game but she arrived to make the yardage that allowed Ireland creep home.

Grace Davitt’s quietly efficient defending kept the number 12 jersey against the Black Ferns and what we all presumed was the best centre in the world. Amiria Rule – the female clone of Ma Nonu – wasn’t even the second best centre in Marcoussis the other day.

Statistical charts

Lynne Cantwell, for her O’Driscoll-like defensive nous, topped all the statistical charts but Murphy’s impact, the sheer relentlessness of her tackling, puts her in the same high performance zone as her pal Katie Taylor.

New Zealand’s entire second-half assault went through Rule and in one memorable moment Murphy not only drove her 94kg opponent backwards but deep into the turf.

“She’s a fantastic player and it was really good to measure myself up against what is one of the better centres in the world. Physically wise I wanted to see where I was. Thought I did okay.”

You landed one cracking hit on her? “Yeah, got one good one. Would have liked to get more but the opportunity didn’t arise. That settled me into the game. Lynne and I were talking loads. There was some really good spacing and line integrity so really happy that way.”

There’s a lingering well of pain she can lower a bucket into. Murphy was injured for last year’s Grand Slam decider in Parabiagio, outside Milan, on St Patrick’s Day.

“Yeah, that is something. I’ll look back on the Grand Slam and it will always be a massive achievement that will make me smile but there will always be that little, slightly bitter taste that I wasn’t on the pitch. Well, I was afterwards, I was screaming and crying! But I didn’t get my hands on the ball. But that happens in rugby.”

Does it motivate you now? “Even though it is a negative there is a silver lining for me; I want to win the Grand Slam again. I want to be on the pitch. I can turn the negative into a positive that way.”

When the black waves began breaking on top of her and Cantwell, all those missed opportunities crystallised into a clear rationale.

“They are not coming through the centres. It is not happening. Just lay them on their ass. They got really big, strong physical runners . . .”

Astonishingly, her rugby career is only five years old. She played lock for the first two seasons. “We had a really good Gaelic and soccer teams over in St Mary’s but it was too social for me, not competitive enough. I saw the rugby girls training and thought I’ll give that a lash. Turned out alright.

College

“When I joined the rugby club in college – I studied in London for two years – they sent me up to Richmond.”

Two games at flanker and she was switched to centre after the briefest stint at fullback.

Not that she was idle before the oval ball took all her attention. An inter-county footballer for Kildare and centre half with Peamount United – where Taylor was a team-mate – hers is an impressive trajectory.

Last spring she asked her Olympic champion friend to present the Irish jerseys. She did. “Katie would be really good friends with some of my good friends. She has been really supportive of woman’s sport in general around Ireland.

“She was such an intelligent soccer player. Scored some ridiculous goals. It’s like how she boxes, really calm, great footwork. Just so controlled.”

We’ve seen that somewhere else. But sometimes getting angry helps.