SHIZUOKA, Japan (AP) — You couldn't pick out the oldest player at this Rugby World Cup as Japan was bringing Ireland back to earth on Saturday.

He was out there, though.

Luke Thompson defied his advancing 38 years with a terrific defensive shift that helped Japan defeat Ireland for the first time, by a 19-12 margin, and kept the Irish scoreless for the last hour in this tournament's biggest boil-over yet.

Thompson was mowing down green jerseys and acting as if the grass was on fire, so quick was he to get up and back into the line. In his energetic 64-minute shift, he made 19 tackles, second only to fellow lock James Moore with 23. Thompson's replacement, Wimpie van der Walt, added six. Neither of the trio missed a tackle.

"I might be out of a job if I do," Thompson said with a smile.

Not bad for 38 either.

"It's only a number, mate."

After seven straight hidings from Ireland, Thompson said there was no magic reason for this huge upset.

"We've worked hard," he said. "We know our game better, got better athletes, and played well tonight. We didn't let Ireland do what they want to do. We did what we wanted."

It also helped that there wasn't as much pressure on them as there was on opening night, when they were favored to defeat Russia. With that experience, and more ball to play with against Ireland, they stuck at a game plan that was more than a year in the making.

They became the first Tier Two team to beat Ireland in a World Cup, and the seven-point margin equaled the most by a Tier Two team over a Tier One, a la Samoa's win against Wales in 1999.

Thompson played every minute of Japan's famed defeat of South Africa in the 2015 World Cup, on that occasion making 13 tackles and 10 carries, and said of this result, "It's right up there. South Africa was amazing and this was truly amazing as well. Everyone had written us off. All the Irish media were talking about South Africa and how they're going to play them in the quarters and what they have to do. We'll just do what we have to do. It's a very special night."

He retired after that World Cup — his third — then answered an emergency call because of injuries to play a one-off test against Ireland in 2017. Then he was watching Japan play Italy in June last year. "I just got the itch. I must have been very animated. My wife (Nerissa) said, 'You want to still be out there?' and I said, 'Yeah, I'd love to be out there,' and she said, 'Why don't you?' and I said, "Nah, its all right.' But she said if I want to do it then she'll support me."

He worked his way into the Sunwolves of Super Rugby and was back playing for Japan in June. It helps that there aren't any big Japanese. All four World Cup locks were born overseas. Thompson came from New Zealand on a rugby exchange and never left. He's played 16 seasons for Kintetsu Liners. He qualified for Japan on residency in 2007 and became a citizen in 2011. But he's retiring for good after this World Cup.

This win over Ireland will be celebrated, he said, but measured.

"We've got a goal to make the top eight and we're not there yet," Thompson said. "In 2015 we won three games and still missed (the quarterfinals). Tonight showed if you're not on your game 100% then you can lose to anyone, so we have to put in an excellent performance against Samoa (next weekend)."

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