In the past, Northampton's Lam has admitted: "I would say in Samoa we almost prefer tackling to running with the ball. We thrive on physical contact." That is why any match involving the South Seas sides - Samoa, Tonga and Fiji - should prove to be a thunderous affair, featuring some of the biggest hits of the tournament.
Lam has made a huge impact on English rugby for other reasons as well, though. He is not just a hard-bodied headcase who feels no pain. His former coach at Northampton, Ian McGeechan, paints a very different picture of the man off the pitch. Almost a pacifist and, contrary to what he does to opponents on the pitch, a great respecter of his fellow men off it.
"He is a big family man, and they are deeply religious as a family," says McGeechan. "Pat is someone who is very concerned about people. When I was leaving the club he rang me from the South Seas, and the day after coming back, he came round to my house to talk to me."
But McGeechan, who left Franklin's Gardens to take up the post of Scotland coach after this World Cup, acknowledges the physical nature of Lam on the park. "He lives for contact. That is because in the South Seas, playing rugby and the physical contact in the game is all part of the warrior experience.
"And they won't waste talent, because they see that as a blessing. A God-given thing."
But Lam, who had played for New Zealand Colts before committing himself to Samoa, is also a thinker. McGeechan adds: "From my point of view as a coach the really good thing with Pat was his excitement about what we were trying to do at Northampton. A lot of what we were trying was new and a step ahead of everyone else. And he is using a lot of it with Samoa."
Someone else who had first-hand knowledge of Lam is John Gallagher, the former All Black full-back now director of rugby at Harlequins. "I knew Pat when he was a 19-year-old," he says. "We were in the New Zealand side at the Hong Kong Sevens in 1989. Off the field he was a shy young man. But on it you could already see that he was an explosive player, either with ball in hand or defending.
"Now at 30 he is a mature international footballer.He adopts a good body angle picking up at No 8. He is very fit. A good support runner picking good lines. I think he is very focused, very committed, and that definitely comes across when you talk to him. He takes his rugby very seriously and is an asset to any team."
McGeechan thinks Lam has improved since he came to Britain, joining Newcastle in 1996 before heading south to Northampton a couple of seasons later.
"He is outstanding," says McGeechan. "I think he has really blossomed since coming to the UK. He is such a good influence, he is so positive about playing and about trying things, and his excitement rubs off on everyone else. There is a buzz and a conviction to him and his play.
"His skill and power at close quarters has really given an edge to everyone at Northampton. He is just an outstanding player, because he can do so many different things and he is so comfortable doing them."
It is Lam's stated intention to retire from the game at international level once this tournament is over, although he fancies two or three more years at club level. He and his fellow countrymen, having reached the quarter-finals in two previous tournaments - 1991 and 1995 - are determined to at least match that, but if possible to improve on it this time around.
They have a few more professionals in the squad now, but none of them needs a financial incentive. For them there is the simple honour of playing for their country.
While no match is actually a battle, Lam and his team-mates are warriors all; and they will play like that. Richter is about to go off his scale.