There are some batters, like Zak Crawley or Michael Vaughan, who owe their England call-ups to their potential. And there are some, like Rory Burns and Dom Sibley, who earn it through weight of runs.
Neither way is necessarily wrong. Vaughan, like Marcus Trescothick and David Gower, went on to enjoy a productive Test career despite a modest county record at the time of his debut. And, while runs at county level are clearly not a guarantee of success at the top level, they remain about as good an indicator as we have.
You can see why a selector would be reluctant to pick Burns, though. Whereas most of the best make batting look a simple, natural process, he makes it look, at times, fiendishly complicated. It seems unthinkable that any coach would suggest a young player copies his method. But, in the end, you can't ignore the returns. It's all about substance over style.
Burns needed this innings. His eight previous Test innings had realised just 78 runs (including three ducks) and, by the time England's tour of India had finished, he had lost his place in the side.
But just as he won his first call-up through weight of runs - he had recorded 1,000 runs in a season for five successive years - he went back to the county game and scored heavily. He has reached 50 seven times in 10 innings in the Championship season. Nobody in the competition has reached 50 as often this year. He earned this recall.
Indeed, Burns earns everything he achieves. Unlike some modern batters, he is prepared to work for his runs. So, while his first 50 took a relatively fluent 90 deliveries, his second took 177.
But that's fine. England have plenty of strokemakers. What they require is someone to provide a platform on which they can build. Burns, who scored 13 runs from the first two-hour session, appears to have the patience for that role.
He is an unusual player in many ways. When his game is in good order, he is unusually tight in that channel around off stump that is traditionally the area to bowl to top-order batters. He rarely pushes at the ball and scored only one of his 17 boundaries - 16 fours and his first six at Test level; a Stokes-esque slog-sweep after he had reached his century - in the 'V' from mid-on to mid-off. That was from a full toss.
New Zealand responded with something approaching modern leg-theory on the second evening, with lots of short-balls and a packed leg-side field. But that only provided scoring opportunities. So, New Zealand settled into a holding pattern: bowling outside off stump in the hope of tempting him into a rash stroke. For a while, Burns ground to something close to a halt.
But he didn't give it away. Unlike some of his top-order colleagues, he was prepared to endure the testing periods in the knowledge that better times would come eventually.
"It was a bit of a grind," Burns admitted later. "They tried to dry me up and bowl at other guys in the order. It was like they were waiting for me to make a mistake. I found it quite difficult to get into a rhythm.
"But we needed those runs today. So, it's nice to contribute. And it's nice to take the opportunity I've been given [on recall].
"You try and stay level. Some days you get good balls. Some days you nick one and get dropped and end up getting a hundred. You have to stay level."
England were grateful for his resistance. Make no mistake, without Burns' century, they were in real trouble here. Nobody else in the top seven made more than 42 and three of them were out for ducks. At 140 for 6, they still required 39 to avoid a follow-on.
As it was, Ollie Robinson sustained his impressive debut with an innings which demonstrated his long-term suitability for the No. 8 position (only Jofra Archer, of recent England seamers, has made a debut as assured as Robinson's with the ball, too). Still, by the time England's ninth-wicket fell, Burns was nine short of his century. He admitted he was "indebted" to James Anderson for helping him reach the milestone. Anderson not only played sensibly, but bravely, taking one on the body in his determination to see Burns home.
There was one passage of play, though, where Burns lost his way. In a session reminiscent of his maiden Test century at Edgbaston in 2019 - an innings in which he was beaten 34 times - he enjoyed a fair slice of fortune in progressing from 77 to 88.
He could - probably should - have been stumped on 77 (when Mitchell Santner saw him coming down the pitch and pushed the ball wider), caught on 88 (when he fenced at one which reared on him from the excellent Tim Southee) and was twice struck on the helmet (once by Southee; once by Kyle Jamieson) as he attempted to hook. He was also fortunate, on 80, to see a top-edged pull fall safely.
You wonder what Australia's fast bowlers, no doubt sent footage by their analysts, will make of such moments. Given the way they bombarded Burns' Surrey teammate, Mark Stoneman, with short deliveries during the last Ashes in Australia, it seems safe to assume Burns will face plenty of the same treatment.
Indeed, you wonder what Australia's seamers will make of this England batting line-up in general. To see Crawley and Dan Lawrence edging to the cordon as they wafted at wide ones, to see James Bracey beaten (albeit by a fine delivery) through the gate and to see Sibley dismissed for his sixth single-figure score in succession (again, by a fine delivery) was hardly the footage to have them quaking in fear. They will also have noted that Ollie Pope, batting on off stump and falling to the off side, has some weakness to exploit and looks especially vulnerable to leg-before dismissals. Really, those Australia seamers will have been quite encouraged by what they have seen.
From an England perspective, it's important to remember that this is the youngest top seven they have ever fielded in a home Test. And they are, give or take, the best players available to England given the IPL absences. They are going to require time and patience to fulfil their talent.
It's a concern, though, and England were grateful for Burns' fight for keeping their heads above water.

George Dobell is a senior correspondent at ESPNcricinfo