Ben Smith, the All Blacks fullback who is supposed to be on sabbatical, is training with the Highlanders and posting personal best scores on the field and gym.

Rather than relax in Wanaka where he has previously enjoyed his holidays, Smith – not due back at the Highlanders until February after cutting short his rugby year in August to rest his body and mind and spend time with his family – is slogging it out in Dunedin with Aaron Mauger's team.

Mauger, the former All Blacks midfielder in his first term as head coach of the Highlanders after returning to New Zealand from Leicester, said the break had done Smith good.

However, he added that the man considered the best No15 in the world can't stay away.

"I think it's the first pre-season he's done since 2011," Mauger told Fairfax. "I think he's enjoying the benefits of it and I think his decision to take that sabbatical and give himself a chance to freshen up, mentally and physically, has been reinforced by the numbers he's pumping out.

"He's managed a couple of [personal bests] in a couple of tests, so hopefully we have him in a great space and ready to roll for the season ahead and he can get out there and feel confident with his body and have another big year."

Smith, 31, a veteran of 64 tests, didn't play the last eight tests of the year and the All Blacks often missed his coolness and game-breaking ability at the back. Damian McKenzie was the All Blacks' fullback in his absence.

"He's on flexi time, so it's up to him at the moment. He doesn't have to be here at all," Mauger told Fairfax.

"But he wants to be in and he wants to be fit for the start of the season. That's his commitment for the team and it's just a good reflection of the character he is and how much he loves this side. That's why he leads this team so well."