Sir Gordon Tietjens has warned his New Zealand Sevens players their Olympic hopes are on the line when they play in the Hong Kong Sevens this weekend.

The World Rugby Sevens Series has given players the opportunity to impress ahead of this summer's Olympics but with just four legs of the tournament remaining, the pressure is increasing as coaches start to contemplate who will make the cut for Rio 2016.

"I've got players that are hungry to be an Olympian," Tietjens said ahead of this weekend's Hong Kong Sevens. "They all want to go to Rio, and every time they go out and they play in that black jersey, it's a performance they want to remember as about what puts them in that team to go to Rio.

"So that's why [Hong Kong] is really important. We can't afford not to play well and the players can't afford not to play well."

Sonny Bill Williams will be in the New Zealand mix this weekend after recovering from a knee injury and he is hopeful of making the final squad for Rio. He is one of a number of players who have attempted to make the transition from XVs to Sevens with an eye on the Games.

"You just cannot make the transition in a short space of time," Tietjens, who is the most successful coach the short form of the game has seen, said. "You've got to play World Series tournaments.

"The game's evolved since the last time a lot of them would have played it. Even Sonny Bill said the other day, this game's a different beast altogether. The conditioning levels are huge."

On Sonny Bill's performances in Sevens, Tietjens added: "He loves the sport. He's a great athlete, he commits himself really well, he's got such a professional work ethic.

"He's a great example for all the other younger players that are coming into the sevens environment and that's what's really special about him: he just sets high standards. It's great for the environment."