Blues coach Pat Lam, who played for Samoa in three World Cups from 1991-99, says Fotuali'i is a catalyst: "He was affected by injury earlier this year but he's a good runner, passer and kicker - his core skills tie together well. Kahn is definitely a missing link - he's tactically aware and his understanding of the game is a perfect fit to run things."
While Fotuali'i is capable of playing at 10 as well, Lam would prefer him at halfback to make the best use of a crisp pass and dynamic running game.
"That's the best spot for him, along the lines of a Piri Weepu or Will Genia."
Former Samoan and New Zealand halfback Ofisa Tonu'u says Fotuali'i makes a key difference: "He's come from that Crusaders factory of success which he can translate into the Samoan camp. I'm surprised Samoa was able to recruit him last year. He would have been in the All Blacks if he'd held on a bit longer. Kahn's got the experience to know when to open it up or keep it tight.
"Take Hamilton on a wet night when they play Wales - to have someone who knows the New Zealand conditions is critical. It's the same when they compete with big forward packs like South Africa. He knows when to rumble it up or clear it through the backline."
In addition to Fotuali'i's rugby brains, other factors are working in Samoa's favour.
"Beating Australia over there would've presented a huge confidence boost," Lam says. "It is also one of the most experienced Samoan teams, they have momentum and now it is time to follow through. The tournament stacks nicely [for them] with Namibia first."
Lam also recognises the hard work of coach Aussie McLean who visited a number of the players' European clubs to convince them their recruits would be looked after and returned in decent condition.
"Getting players released from European clubs is a big thing," Lam says. "World Cup year is when Samoa is strongest. Normally professional rugby is good for players' financial welfare but not the country when it comes to availability; it's a bit like recruiting a Kiwis rugby league team - but with a World Cup, the teams gets plenty of time together preparing and it makes a difference."
Even with home advantage, valuable momentum and decent availability, Tonu'u still harbours one slight concern in the big games: "In the past, they might only get 30 per cent possession - it depends how they deal with that. When they play South Africa and Wales they could be vulnerable to indiscipline and yellow cards. That can be a threat - it's all about keeping cool heads."