Two-time Rugby World Cup winner Sonny Bill Williams is on a new journey.

The All Black is now heading into his fourth HSBC World Rugby Sevens Series round, and has one eye on the Olympic Games. Having made his debut on home soil in Wellington, where Gordon Tietjens' side were victorious, Williams has also played in Sydney and Hong Kong, with Singapore coming up this weekend.

"I have always wanted to play sevens" said Williams. "I met Titch five years ago and we had a chat then. When the Olympics came about I was always going to throw my name in the ring.

"I was pretty nervous because I knew how taxing it was on the lungs but I learn through actions so playing and training. It was tough, I needed to get a lot fitter but have enjoyed the challenge. I have enjoyed coming into an environment where there are a lot of world class players to learn from.

"Titch's sessions are gruelling, he is his own man and he has his own techniques and sometimes you have to bite the bullet and get on with things. It has been tough but I am loving the environment and I am loving sevens."

In his three tournaments so far Williams has been on the winning side twice, and finished as a runner-up in the other (last weekend in Hong Kong).

His transition has been helped too by close friend Liam Messam who has returned to the sevens after a long absence and who will also captain the New Zealand side this weekend in the absence of Scott Curry, Tim Mikkelson and DJ Forbes.

"First was in Wellington, I was chucked straight in there. After that I felt so much at ease as a sevens player. I am quite pleased with where I am at, but being involved with good blokes has really helped. I am not shy about asking the questions when trying to improve and the guys have been great at that."

There are now just three rounds left on the 2015-16 series and less than four months until rugby sevens' makes its debut at the Olympic Games. As the reason Williams made the switch into the sport, what will it take to get on the plane?

"The end goal is to be part of the Rio squad," added Williams.

"In saying that from an individual point of view I just want to do my best, I love the challenge. To be a part of it I need to make sacrifices, keep it simple, and be the best I can be and not worry about making it, you know.

"If I make it I make it but the key is to be a good team man, and I guess time will tell."