Gradually grooming a young prospect against the world’s best scrummagers has obvious upside.

Selections: Siale Lauaki and Ollie Norris.

Fourth hooker and halfback

Specialist positions demand specialist depth. Rennie sent Noah Hotham a firm message about speed to the base by including Crusaders deputy Kyle Preston over him for the July window.

With a fourth halfback now needed, though, Hotham’s running threat can’t be overlooked.

The All Blacks are well served at hooker, as Asafo Aumua pushes Codie Taylor for minutes and Samisoni Taukei’aho waits in the wings. Geroge Bell appears likely to be recalled as the fourth in line. Highlanders and Southland hooker Jack Taylor is the other option.

Selections: Noah Hotham and George Bell

Locks

Fabian Holland will return from the shoulder surgery that ruled him out of the entire Super season. After minimal rugby he will, however, require gradual reintegration to the test scene, which could necessitate the All Blacks carrying a sixth lock, particularly with Tupou Vaa’i expected to spend further time at blindside flanker after his successful switch there against Ireland.

With Scott Barrett sidelined, likely for the remainder of the year, Jamie Hannah is the next cab off the rank to continue his development, after debuting off the bench in the test opener against France.

Christchurch-raised Chiefs lock Fiti Sa’s 2.03m frame is on the national radar after training with the All Blacks in week one but the 23-year-old’s time is likely to come down the line.

Selections: Fabian Holland and Jamie Hannah

Loose forwards

As always, this is where it gets interesting.

Despite losing Devan Flanders, Dalton Papali’i and Hoskins Sotutu abroad, New Zealand’s loose forward stocks remain stacked with established and fast-emerging talent.

The number of loosies added to the July squad will depend on whether Rennie and his selectors opt for a 6/4 or 7/3 split.

Du’Plessis Kirifi is the obvious candidate to be recalled after missing out to Anton Segner but if the squeeze comes on, it may not be that simple.

With Luke Jacobson, Segner and Ardie Savea options at openside, Kirifi’s lack of versatility as a specialist No 7 could potentially hurt his case.

Highlanders rookie of the year Lucas Casey has strong claims after his breakout season. The dynamic 23-year-old is well in the frame after attending the All Blacks’ non-Super finalists camp – and he will only improve as he adds bulk and matures.

Crusaders No 8 Christian Lio-Willie and Moana Pasifika counterpart Semisi Tupou Ta’eiloa are other contrasting options – the first a workhorse, the second a destructive ball carrier – if Rennie is seeking cover at the back of the scrum.

Personally, I believe selecting Casey carries the most upside. It’s a matter of when, not if, he features for the All Blacks. Exposing him to South African opposition could prove invaluable for his long-term development. And by next year’s World Cup, he could be a weapon off the bench.

Should injuries hit the loose forwards on tour, Rennie could potentially request an exemption to recall Shannon Frizell once he returns for Tasman.

Selections: Lucas Casey/Du’Plessis Kirifi

Midfield

Rieko Ioane’s recall will further bolster depth in an area that has most elements covered. Like Anton Lienert-Brown, Quinn Tupaea and Jordie Barrett, Ioane’s versatility as a centre/wing option is favourable on a tour such as this.

Highlanders co-captain Timoci Tavatavanawai offers a point of difference with his power and jackling strengths but his lack of pace could count against him.

Selections: Rieko Ioane and Timoci Tavatavanawai

Outside backs

With Caleb Tangitau (definitely) and Leicester Fainga’anuku (likely) ruled out due to injury, the options are somewhat limited.

Emoni Narawa fits the brief, particularly for the aerial assault that awaits, but he has played little rugby of late after fracturing a bone in his foot earlier this year.

Chiefs fullback Isaac Hutchinson is another compelling option but he, too, missed the Super final through injury and his return is unknown at this stage.

Selections: Emoni Narawa (if fit)

Liam Napier is a Senior Sports Journalist and Rugby Correspondent for the New Zealand Herald. He is a co-host of the Rugby Direct podcast.