In this season's Premiership media guide Northampton's squad list is written in comically tiny print. They have crammed 56 names in there, practically everyone they know. It is as if they are declaring that after the falling away of their challenge in the last two games of last season, squad depth is not going to be a problem.

Never has Soane Tonga'uiha looked so small, squeezed alongside all the other names in six-point. As if to reassure us, though, his weight is listed as 133 kilograms, the best part of 21 stone, and as he approaches after a midweek training session he looks every pound of that.

Squad depth is a poignant subject when it comes to discussing Tonga'uiha and his size. The Tongan was one of four Saints who started 32 matches last season. That would be one thing if he were a fly-half, but for a prop carrying that sort of ballast it is simply heroic. There is no chance of him starting 32 games this season (he started 31 the season before last). Northampton have more options at prop. At some point, the 29-year-old is going to take a rest.

He smiles at the thought. "As much as I would like to think that would help me later on," he says, "I will be frustrated," he says. "It's probably selfish of me to want to play throughout the whole season, but what would worry me is if whoever steps in has a blinder. How long would it be before I get a chance to prove myself again?"

"Not very" is surely the answer in a season that incorporates the World Cup, Six Nations, LV Cup, Aviva Premiership and a Heineken Cup pool containing Munster, the Scarlets and the high-flying Castres. If Saints are to make it to Twickenham in May for the Heineken Cup final or the Premiership final, no prop will have played every game. The memory of last season's collapse against Leinster, in the second half of a Heineken Cup final they had been leading by 16 points, will ensure such demands are not made again.

"We were tired," confesses Tonga'uiha. "I don't like to admit to it. But because of the occasion we were going on adrenaline for the first half and the whole season took its toll in the second."

Since then, he has spent much of his time on World Cup duty with Tonga. The islanders were given overwhelming ovations wherever they went in New Zealand. Theirs was the honour of facing the All Blacks in the opening game. It was a return to the city where Tonga'uiha had spent most of his life, having moved to Auckland from Tonga as an eight-year-old. Eden Park was where he first played first-class rugby, and a few old team-mates — Keven Mealamu, Jerome Kaino and John Afoa — were playing for the All Blacks.

"I got too emotional for that game," he says. "We were running around like headless chickens. It's the biggest stage of my career, at my home ground. I'd left because I couldn't get a Super 12 contract. I wanted to prove how far I'd progressed, but in that situation you tend to forget about your role in the team. You try to do too much and end up doing nothing."

Tonga lost credibly, but then put out a second team against Canada and lost that too. Their first team was too strong for Japan and, in the upset of the World Cup, they beat France in their final pool game. We all know how close France came to winning the whole thing.

"I'd be lying if I said I hadn't thought about that. If we'd beaten France with a bonus point we would have qualified ourselves, but we weren't interested in that. We just wanted to win. Losing against Canada and not getting a bonus point against Japan were the missed opportunities, but if we had succeeded there France would have had a different mentality against us. Our win woke a sleeping giant."

Still, that was two giants slain, in statistical terms. A nation of 100,000 beat nations of 128m and 62m respectively. The rugby achievements of the Pacific islands continue to astonish. "We're naturally big people and we all love our food, so we keep getting bigger. In Tonga on any clear space there are people playing touch rugby every day, which is how we develop our skills. When we get picked up by a professional side all we have to do is work on our fitness."

Tonga'uiha adds his voice to the many that urge the International Rugby Board to relax the rules of eligibility, so ex-All Blacks or Wallabies might play for their native islands after a stand-down period. Forget the islanders, though. Tonga'uiha has lived in England for six years, is married to a girl from Bedford and has qualified for his British passport. He is also 21st and can play 32 games a season. There are a few island nations in the North Atlantic who could do with a specimen like that.