Josh Ioane called in to All Blacks for Tonga Test to cover injured Richie Mo'unga

Highlanders first-five Josh Ioane could be in line to earn his first All Blacks cap after being called in to the squad for Saturday's Test against Tonga as injury cover for Richie Mo'unga.

Ioane missed out on selection for the Rugby World Cup with coach Steve Hansen opting for just two first-fives in his squad of 31, but Mo'unga's shoulder injury sustained in the All Blacks' Bledisloe win at Eden Park last month will keep him on the sideline this weekend.

The injury has seen the All Blacks call in Ioane who was named in the wider squad earlier this year.

Ioane was close to making his Test debut during the Rugby Championship when he was named on the bench for the All Blacks' clash with Argentina in Buenos Aires, but with the scoreline close Hansen opted not to use him as he didn't want to throw Ioane into a pressured environment.

"He's getting a lot of learning, and we'll put him out there when we think he's ready to rock and roll," Hansen said after the 20-16 win in July.

"It wouldn't have been fair to put him out [against Argentina], lose the Test match and then everyone starts pointing their fingers at a young kid because he's steering the ship.

"We didn't want that to happen, so we didn't put him on.

"I'm sure from what we've seen last week, and what we'll see this week, eventually he'll get a game."

Saturday's Test in Hamilton is the All Blacks' final Test before the Rugby World Cup and Hansen plans to name a top side, having previously said resting "front-liners" in Hamilton will leave players without enough rugby action heading into the team's opening World Cup match against the Springboks.

"First and foremost we've got to get game time into a large proportion of the squad - too long a gap otherwise between the last game and the first game at the World Cup," Hansen said.

"So this will create a two-week window which is acceptable."

This season, Mo'unga has played first-five with Beauden Barrett shifting to fullback to create a dual playmaker system in the backline. While it got off to a rocky start in Wellington against the Springboks, the All Blacks persisted with the scheme and started to reap the benefits at Eden Park before Mo'unga was injured.

Whether that means Beauden Barrett will slot back into first-five and allow an outside back such as Ben Smith to play fullback or Ioane play at flyhalf with Barrett retaining the No. 15 jersey remains to be seen.

Hansen names his line-up on Thursday morning.