Whether it is wider squad or game day decisions, a myriad of factors come into any equation.
Form, fatigue, injuries, character, squad harmony; a holistic approach is often adopted.
Take rookie All Blacks lock Josh Lord, a genuine bolt from the bluethat had even the most ardent New Zealand rugby followers doing double takes after he received his boarding pass for the northern tour.
Other than fellow Chiefs lock Tupou Vaa'i's fast-tracked rise last season – after beginning the year labouring with his father in Auckland – the All Blacks rarely take punts on unproven prospects, particularly in the tight-five where athletes develop much later than their peers.
With established locks Scott Barrett and Patrick Tuipulotu returning home after the All Blacks' Rugby Championship-winning campaign, the next obvious candidates were Highlanders and Tasman second-rower Pari Pari Parkinson and Crusaders contender Quinten Strange.
Parkinson loomed as the next best available lock. With Tasman since 2016, and the Highlanders and New Zealand Māori for the past three years, Parkinson has been earmarked for the All Blacks for some time.
A huge lump at 2.04m and 119kg, Parkinson appears readymade for test rugby. He's a tall lineout target and an imposing presence. Only, that's not quite the full picture at this stage.
Parkinson has physically manhandled opponents to standout during this year's NPC but he's struggled to string consistent games together in his career and, therefore, battled to compile a compelling body of work after regularly breaking down.
The other issue comes around something of a boozy culture among sections of players in the Highlanders during the past few years that has seen several players – five this year following a party at Josh Ioane's house - reprimanded for off-field incidents.
In these such instances, lad culture has failed to recognise it's not enough to perform on the field. Off field expectations must also align, particularly when pursuing higher honours.
Prior to naming their Rugby Championship squad - and approaching a 14-week tour like no other - the All Blacks set out their stool that off-field character would have elevated importance given there were no guarantees players could be replaced due to the closed border and MIQ logjam.
In considering Parkinson, his durability was in question which, in the case of injury, could leave the All Blacks exposed to carrying three fit locks. And while he's believed to have improved off the field, there remains an element of proving himself in this regard too.
With the All Blacks largely confined to soft quarantine restrictions for the duration of their tour, both elements heightened his risk profile.
At 25-years-old Parkinson may yet mature into a prospect that's the right fit for the All Blacks. But he was deemed not right for now.
Strange was the other candidate, having been called into the All Blacks camp last year only to suffer an ankle injury at training. He, too, has issues with his body – a shoulder issue the latest ailment he recently recovered from.
The other factor with Strange is his long-term development prospects at the Crusaders. Only last year he opted to re-sign with the Crusaders around the same time All Blacks centurion Sam Whitelock, Barrett and Mitchell Dunshea extended their deals through to 2023.
The Crusaders don't rotate their top side nearly as much as other New Zealand teams, with Whitelock and Barrett starting every match of importance, which leaves Strange bound to the bench or not even in the squad.
This is another aspect that tipped the upside in Lord's favour. Next year he is guaranteed to see plenty of game time at the Chiefs alongside Brodie Retallick and Vaa'i.
To this point, Lord has played five games for the Chiefs but the All Blacks tracked him long before he reached Super Rugby.
The 20-year-old was well ahead of others in age-grade teams and displayed a dedicated training ethos, big heart and a desire to go to dark places when competing within a Super Rugby environment.
The All Blacks know they need to add at least another five kilograms to Lord's frame to help him cope with the brutality of the test arena but by exposing him to their world-class training and nutritional experts in the coming weeks, they can significantly accelerate his development.
Vaa'i was a man among boys during his time with the New Zealand under 20s and he showed last year, in starting his second test against the Wallabies, he was ready for that stage. On the northern tour the 21-year-old, who has now played seven tests, will play a big role as third-choice lock.
From a mentality perspective, Lord is thought to be not far off his Taranaki team-mate.
When he gets his chance in Europe, possibly against Italy in Rome, Lord won't be asked to do anything special. Push, jump, tackle will be his simplistic brief.
Come next year the All Blacks will then hope to witness the benefits of their calculated selection punt that caught everyone by surprise.