New Zealand Rugby's retention of the top tier of players continues at pace.

First-five Lima Sopoaga has become the 20th current or recent All Black to re-sign beyond the 2017 Lions tour.

Steve Tew said players are constantly competing against the best and want to to push themselves to the highest level.

"That's what works for us, a good comparison is New Zealand rowing. We're very good at that sport, because they go to Karapiro and race against each other, they're always racing against the best in the world at home."

Tew said players want to stay and push their All Black claims, "and he won't be the only one who's got an aspiration, which is fantastic for us."

"I think one of our strengths is that competition for positions."

The good news continues for the New Zealand Rugby Union, with Tew confirming that All Blacks assistant coach Ian Foster and scrum guru Mike Cron have both recommitted through until 2017.