World Cups are traditionally based around defence and Williams is one player who can unlock the tightest of screens with his offloads.
"It's just more fitting into the team role, the team play," Williams said. "I guess I'm just toning it down a bit. Sometimes I get a bit too excited out there on the field."
Henry's message to Williams was clear. "Don't try and do it all in five minutes," Henry said. "The game lasts for 80. He played pretty well in South Africa, I thought, but I think players are inclined to, when they get a chance and they haven't played for a while, to try to push it too much and probably overdo it. I guess patience is going to be key and, if he just lets his natural ability control the way he plays, I think he will play well."
Williams said he was confident the new midfield combination with Nonu would work well as there had been a lot of different combinations tried at training in the past month. "Me slotting into 12 and him at 13 is no biggie. We each understand the roles," he said.
Williams was picked ahead of Smith purely to give Williams game time and the selectors are well aware of what Smith can do. Henry said Smith would return to play Japan next weekend.
"The reason was to give Sonny Bill an opportunity and he's got that," Henry said. "We don't know what's going to happen later in the tournament and who's going to be standing and who's not. We have to give players opportunities to play and force their abilities on the selectors. And also if we have injuries guys need to have had game time in recent times.
The midfield mix isn't the only change from the selectors, with Isaia Toeava and Richard Kahui on the left and right wings, Jimmy Cowan starting at halfback and Israel Dagg at fullback.
Kahui said getting the call-up was particularly satisfying given his ongoing problems with shoulder injuries.
"To be here now in a World Cup squad and starting a World Cup game means a lot. When I look back over the last 12 months and having the operation and coming back - it's been a bit of a ride.
"My preference is still 13 but I'm very comfortable on the wing. I don't have express pace but I have other attributes: I'm solid under the high ball, my work rate and I'll chase kicks until the 81st minute."